hi my character and the moving platform are jitter when the character is jumping on the platform. What can i do against it?
What do you mean by " are jitter "?
can you show me a screenshot so I can understand better your problem :)?
its not moving smoothly. It moving from one point to another but the platform is shaking a little bit during the movement
Ok, I do understand you beter 
Could you please post the code of your platform? so I can check what is happening 
I had a similar problem with some moving platforms in my game. Try changing the Interpolate property of the rigidbody to ‘Interpolate’. That seemed to smooth it out for me.
I actually had this problem. If you are using the prebuilt character controller, uncheck the box that says “Used Fixed Update”. My jittering occured because one object (The platform) was updating at a normal rate while the other (The Character Controller) Was updating at a different rate.
Where is this Used Fixed Update parameter ?