Only the top of my cylinder can move with bone.

I have a problem, hope you can help me.
Only the top of the cylinder will move when I rotate the bone in the pose mode.

As the picture,I’m sure the cylinder is in the envolope.
I’m also sure the cylinder is attched with armature modifier.

The bones move vertices. The only vertices I can see are the ones at the end which are moving. You need to add more geometry if you want other parts to also move. Ctrl+R adds edge loops

Oh! Thank you! You sove my problem! Thank you a lot!!