it can work now!!! thank you Shiu!!!
appearM_.state.Complete += uncleMAppearAnimationEndCallBack;
private void uncleMAppearAnimationEndCallBack(object sender, Spine.CompleteArgs e){
appearM_.skeleton.SetToSetupPose();
appearM_.state.SetAnimation(0, "BM_appear_down", false);
//appearM_.loop = true;
StartSceneController controller = Camera.main.GetComponent<StartSceneController>();
if(controller != null){
controller.flyInPlaying = true;
}
appearM_.state.Complete -= uncleMAppearAnimationEndCallBack;
}