Abstract: In order to suppress the phase noise and overcome the deficiencies of integer frequency and fractional frequency technologies, a fractional frequency synthesizer design proposal based on ΣΔ modulation was proposed, and the performance of the design proposal was emphatically analyzed. The simulation showed that the solution can effectively solve the problem of frequency spur, can effectively suppress the phase noise of the frequency synthesizer in the medium frequency offset, so it is expected to be widely applicable in RFID systems.