SU-27 stick shaking

I am using ch fighter stick.

When i use su-27, i see my controller shakes constantly. I don't have this problem with other planes.

additionally, plane always tends to roll to a side. sometimes left or sometimes right. trimming doesn't solve problem.

and lastly, when i engage H autopilot alt hold, plane shakes like crazy.

Sounds like the centre position of your stick might be worn. Try using a small dead zone for pitch & roll and see if that makes a difference. Also make sure your stick is properly calibrated using the CH control manager.

I am using ch fighter stick.

When i use su-27, i see my controller shakes constantly...

and lastly, when i engage H autopilot alt hold, plane shakes like crazy.

The two might actually be unrelated. The stick shaking means that you have to add a bit of "dead zone" into the axis in the Options menu. There seems to be a little bit of spiking with your stick. If you go into the Su-27 Controller settings (under Options), select Axes and, then, "Fine Tune" (I think that's what it's called). Expand the deadzone and you should be good.

The autopilot business is unrelated if it only happens when you're flying at less than roughly 550 km/hr. It's a known issue which will, hopefully, be fixed in the not to distant future.

i have already added deadzone it doesn't help. and i don't see this with other planes like mig29 or su33

Turn off FFB in options and check for double axis binding.