We have tested CYUSB3065 wth 720 at 60 fps, this works fine. Theoretically the CX3 can support data upto around 240 MBps. In your scenario the image data will be around ~210 MBps , but further you will need to add headers and there will be some associated switching latencies which will decrease the data-speed. So, I would say that driving CX3 at 120 fps -720p will be difficult to implement.
In order to realize 720p 120fps，whether there are other solutions？For example, image compression（H.264,MJPEG）.And whether there are available compression algorithms or compression library（or Ipcore） available?
You would need to use an Image sensor for the compression part.
You can have a look at this (http://www.cypress.com/documentation/development-kitsboards/ascella-cypress-cx3-thine-isp-13mp-reference-design-kit-rdkdesign) for streaming 720p @ 120fps.
This RDK is based on Cypress’s EZ-USB® CX3™ USB 3.0 camera controller and THine’s THP7312 image signal processor (ISP).
Thank you,I got it,but is there any other ISP solutions recommended.