diff --git a/doc/apis.adoc b/doc/apis.adoc
index b633081d..94c81932 100644
--- a/doc/apis.adoc
+++ b/doc/apis.adoc
@@ -100,6 +100,7 @@ transaction, make sure to specify a `volumeClaimTemplate` that so that the same
 |=======================
 | Field  | Description |Scheme| Required
 | `replicas` | Replicas is the actual number of replicas for the application | int32 | true
+| `selector` | selector for pods, used by HorizontalPodAutoscaler | string | true
 | `hosts` | Hosts that route to the application HTTP service | []string | true
 | `pods` | Status of the pods | []<<podstatus>> | true
 | `scalingdownPods` | Number of pods which are under scale down cleaning process | int32 | true