Like, I use a state controller, Ctrl1, to drive state-driven, which as following hierachy
CM stateDrivenCam
-Vcam1
-Vcam2
Certainly the Ctrl1 could control the state, but if I want to add some flavor to it. For example, I want to animate Vcam1, then I tried to use Ctrl1 to control both state-driven cam and Animation Clip, but failed.
Seems like cinemachine gives the animation controller more priority to get Vcam1 position , rather than play the animation… Or just my guess…
So, is there a proper way to animate Vcam?
I don’t really understand your question. What effect are you trying to achieve?
Sorry for the missing message !
I eventually use timeline to drive the 1st Vcam to control the camera intro, using playable director to control the whole, which works pretty well 
My goal is to animate a state-driven vCam when it is activated. I tried animation clip on Vcam, but it turns to rattle the camera…
In general, if your vcam is doing procedural motion (i.e. animating its own position or rotation to follow a target object), then you cannot also animate its transform in other ways, because the 2 motions will fight. You have to do one or the other, but not both.
You can animate a vcam that has “Do Nothing” in Aim and Body, and blend between that vcam and other vcams.