Abstract: Aimed at the constant voltage output of the AC envelope modulation wireless power transfer system, through the analysis of the series/series type AC envelope modulation wireless power transfer system model, the constraint relationship that keeps the system output voltage constant was obtained. Choosing to add an improved AC-AC Boost converter on the primary side to realize the constant voltage output of the system, the control logic of the converter was analyzed and designed. By building a simulation model, simulation verified the feasibility of the designed system. Simulation shows that the AC envelope modulation wireless power transfer system designed in this paper can not only meet the requirements of constant voltage output, but also has the advantages of low harmonics and high power factors.