if i go on a modal analysis，how can i output the modal of the viberation ？

The output from a "modal analysis" consists of:

a) the natural frequencies
b) the mode shapes

Both of the above are available in numeric reports. However, it is more informative to "animate" the mode shapes.

i have got what you mean，but i want to check the mode shape as a picture，is there any way i can go？

Yes, use the "animation" option. Then, you can request a "print preview", which will stop the motion - but show all the positions of that mode.

the “print preview ”in my software can not be used，is there anything wrong with my caesar2 ？