A high-power sweep frequency microwave source of magnetron based on injection-locking theory is proposed to meet the requirements of variable frequency microwave heating, communication jamming and other fields. The theoretical analysis of the equivalent circuit model of magnetron is conducted in the first place. Then, the model of Continuous-Wave(CW) magnetron is established in CST STUDIO SUITE to work on the simulation verification of particle-in-cell. The effects of injection ratio on magnetron RF voltage and spectrum are analyzed at last. And the maximum sweep bandwidth of magnetron output turns out to be 21 MHz.