This paper analyzed the performance of existing UHF frequency modulator, and a UHF frequency modulation circuit based on SAW one port resonator was designed. The design idea was presented in detail. First, SAW one port resonator design was optimized. Then frequency modulation circuit was optimized. The varicap diode was used to modulate the frequency directly, thus the circuit has the features of simple structure, stable center frequency and easy test. It suits kinds of wireless communication equipments in low and median such as wireless microphone, wireless intercom, wireless headset, wireless remote control, wireless data acquisition, etc.