diff --git a/pyzoo/zoo/serving/client.py b/pyzoo/zoo/serving/client.py
index d9eb51a297d..599ec0cfa6f 100644
--- a/pyzoo/zoo/serving/client.py
+++ b/pyzoo/zoo/serving/client.py
@@ -101,8 +101,16 @@ def enqueue(self, uri, **data):
         field_list = []
         data_list = []
         for key, value in data.items():
+            if "string" in key:
+                # list of string will be converted to Tensor of String
+                # use | to split
+                str_concat = '|'.join(value)
+                field = pa.field(key, pa.string())
+                data = pa.array([str_concat])
+                field_list.append(field)
+                data_list.append(data)
 
-            if isinstance(value, str):
+            elif isinstance(value, str):
                 # str value will be considered as image path
                 field = pa.field(key, pa.string())
                 data = self.encode_image(value)
diff --git a/zoo/src/main/scala/com/intel/analytics/zoo/pipeline/inference/InferenceModel.scala b/zoo/src/main/scala/com/intel/analytics/zoo/pipeline/inference/InferenceModel.scala
index d29dc7515e1..b3b4eb273c6 100644
--- a/zoo/src/main/scala/com/intel/analytics/zoo/pipeline/inference/InferenceModel.scala
+++ b/zoo/src/main/scala/com/intel/analytics/zoo/pipeline/inference/InferenceModel.scala
@@ -24,9 +24,11 @@ import java.util.{List => JList}
 
 import com.intel.analytics.bigdl.nn.abstractnn.Activity
 import com.intel.analytics.bigdl.tensor.Tensor
+import com.intel.analytics.bigdl.tensor.TensorNumericMath.TensorNumeric
 import com.sun.xml.internal.bind.v2.TODO
 
 import scala.collection.JavaConverters._
+import scala.reflect.ClassTag
 
 class InferenceModel(private var autoScalingEnabled: Boolean = true,
                      private var concurrentNum: Int = 20,
@@ -37,7 +39,6 @@ class InferenceModel(private var autoScalingEnabled: Boolean = true,
 
   require(concurrentNum > 0, "concurrentNum should > 0")
 
-  private var batchCnt: Int = 0
   @transient var inferenceSummary: InferenceSummary = null
   /**
    * default constructor, will create a InferenceModel with auto-scaling enabled.
@@ -743,17 +744,17 @@ class InferenceModel(private var autoScalingEnabled: Boolean = true,
     val model: AbstractModel = retrieveModel()
     try {
       val begin = System.nanoTime()
-      val batchSize = if (inputActivity.isTensor) {
-        inputActivity.toTensor[Float].size(1)
-      } else {
-        val sampleKey = inputActivity.toTable.keySet.head
-        inputActivity.toTable(sampleKey).asInstanceOf[Tensor[Float]].size(1)
-      }
+//      val batchSize = if (inputActivity.isTensor) {
+//        inputActivity.toTensor[T].size(1)
+//      } else {
+//        val sampleKey = inputActivity.toTable.keySet.head
+//        inputActivity.toTable(sampleKey).asInstanceOf[Tensor[T]].size(1)
+//      }
       val result = model.predict(inputActivity)
       val end = System.nanoTime()
 
       val latency = end - begin
-      val name = s"model predict for batch ${batchSize}"
+      val name = s"model predict for batch"
       InferenceSupportive.logger.info(s"$name time elapsed [${latency/1e9} s, ${latency/1e6} ms].")
 
       result
diff --git a/zoo/src/main/scala/com/intel/analytics/zoo/serving/engine/FlinkInference.scala b/zoo/src/main/scala/com/intel/analytics/zoo/serving/engine/FlinkInference.scala
index 06838c94dee..2448281a876 100644
--- a/zoo/src/main/scala/com/intel/analytics/zoo/serving/engine/FlinkInference.scala
+++ b/zoo/src/main/scala/com/intel/analytics/zoo/serving/engine/FlinkInference.scala
@@ -36,8 +36,6 @@ class FlinkInference(params: SerParams)
 
   override def open(parameters: Configuration): Unit = {
     inferenceCnt = 0
-    model = params.model
-//    println("in open method, ", model)
     logger = Logger.getLogger(getClass)
     pre = new PreProcessing(params)
   }
diff --git a/zoo/src/main/scala/com/intel/analytics/zoo/serving/preprocessing/PreProcessing.scala b/zoo/src/main/scala/com/intel/analytics/zoo/serving/preprocessing/PreProcessing.scala
index 697a83575fe..65d652235a4 100644
--- a/zoo/src/main/scala/com/intel/analytics/zoo/serving/preprocessing/PreProcessing.scala
+++ b/zoo/src/main/scala/com/intel/analytics/zoo/serving/preprocessing/PreProcessing.scala
@@ -62,20 +62,31 @@ class PreProcessing(param: SerParams) {
     val instance = Instances.fromArrow(byteBuffer)
 
     val kvMap = instance.instances.flatMap(insMap => {
-      val oneInsMap = insMap.map(kv => {
-        if (kv._2.isInstanceOf[String]) {
+      val oneInsMap = insMap.map(kv =>
+        if (kv._1.contains("string")) {
+          (kv._1, decodeString(kv._2.asInstanceOf[String]))
+        }
+        else if (kv._2.isInstanceOf[String]) {
           (kv._1, decodeImage(kv._2.asInstanceOf[String]))
         } else {
           (kv._1, decodeTensor(kv._2.asInstanceOf[(
             ArrayBuffer[Int], ArrayBuffer[Float], ArrayBuffer[Int], ArrayBuffer[Int])]))
-        }
-      }).toList
+        }).toList
 //      Seq(T(oneInsMap.head, oneInsMap.tail: _*))
       val arr = oneInsMap.map(x => x._2)
       Seq(T.array(arr.toArray))
     })
     kvMap.head
   }
+  def decodeString(s: String): Tensor[String] = {
+
+    val eleList = s.split("\\|")
+    val tensor = Tensor[String](eleList.length)
+    (1 to eleList.length).foreach(i => {
+      tensor.setValue(i, eleList(i - 1))
+    })
+    tensor
+  }
   def decodeImage(s: String, idx: Int = 0): Tensor[Float] = {
     byteBuffer = java.util.Base64.getDecoder.decode(s)
     val mat = OpenCVMethod.fromImageBytes(byteBuffer, Imgcodecs.CV_LOAD_IMAGE_UNCHANGED)
diff --git a/zoo/src/test/scala/com/intel/analytics/zoo/serving/InferenceSpec.scala b/zoo/src/test/scala/com/intel/analytics/zoo/serving/InferenceSpec.scala
new file mode 100644
index 00000000000..6d254d55b25
--- /dev/null
+++ b/zoo/src/test/scala/com/intel/analytics/zoo/serving/InferenceSpec.scala
@@ -0,0 +1,36 @@
+/*
+ * Copyright 2018 Analytics Zoo Authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.intel.analytics.zoo.serving
+
+import com.intel.analytics.bigdl.tensor.Tensor
+import com.intel.analytics.zoo.serving.utils.{ClusterServingHelper, SerParams}
+import org.scalatest.{FlatSpec, Matchers}
+
+class InferenceSpec extends FlatSpec with Matchers {
+  "TF String input" should "work" in {
+//    val configPath = "/home/litchy/pro/analytics-zoo/config.yaml"
+    val str = "abc|dff|aoa"
+    val eleList = str.split("\\|")
+//    val helper = new ClusterServingHelper(configPath)
+//    helper.initArgs()
+//    val param = new SerParams(helper)
+//    val model = helper.loadInferenceModel()
+//    val res = model.doPredict(t)
+//    res
+  }
+
+}
diff --git a/zoo/src/test/scala/com/intel/analytics/zoo/serving/PreProcessingSpec.scala b/zoo/src/test/scala/com/intel/analytics/zoo/serving/PreProcessingSpec.scala
index c11bcda4b29..956ae21f26a 100644
--- a/zoo/src/test/scala/com/intel/analytics/zoo/serving/PreProcessingSpec.scala
+++ b/zoo/src/test/scala/com/intel/analytics/zoo/serving/PreProcessingSpec.scala
@@ -58,4 +58,12 @@ class PreProcessingSpec extends FlatSpec with Matchers {
     val a = pre.decodeTensor(info)
     a
   }
+  "decode string tensor" should "work" in {
+    val pre = new PreProcessing(null)
+    val str = "abc|dff|aoa"
+    val tensor = pre.decodeString(str)
+    assert(tensor.valueAt(1) == "abc")
+    assert(tensor.valueAt(2) == "dff")
+    assert(tensor.valueAt(3) == "aoa")
+  }
 }