Abstract: This paper introduces a high precision amplitude control method based on 2 bit step-wave time- modulation. The theoretical model of 2 bit step-wave time-modulation is established, and the influence of the stepped waveform on the amplitude control accuracy of RF signal time modulation is analyzed. A 2 bit step-wave time modulation circuit is designed and verified by high-precision amplitude control experiment. The measured results show that the 2 bit step-wave time-modulation circuit achieves an attenuation dynamic range of 0-31.75 dB and a 7 bit amplitude control at 40 MHz signal bandwidth, while the root mean square error is 0.07 dB with an error range within ± ( 0.1 + 0.8 % AS ) dB.