Abstract: X-band frequency synthesizer is one of the key techniques of multi-function radar, and it affects radar＇s main performance directly. Based on essential theoretics, the way of implementation of X-band frequency agility synthesizer is presented in this paper. The main factors, such as phase noise, spur, agile time are discussed. Finally,detail design project is described, along with the test and measurement restdts, which verify that the synthesizer achieves integrated system requirement. The synthesizer based on the method described in this paper has been used in several radar systems, and it has been proved to enhance the anti-interference ability of radar.