A monocycle power factor correction method is based on a voltage booster circuit and a system main control chip and includes the following steps: (1) judging whether soft start ends, if so, directly entering step (2); or adding an output voltage reference value Uref, then entering step (2); (2) reading a bus voltage sampling value Uo and an inductance and current sampling value ig according to A/D sampling triggering time; (3) calculating the PWM signal cycling rate of a drive switching tube; (4) outputting a PWM signal according to the PWM signal cycling rate; (5) calculating the A/D sampling triggering time of next time according to the signal cycling rate; (6) returning to step (2).Without using the traditional power factor correction circuit and special monocycle PFC chip, the invention only needs to integrate the method software in the main control chip of the existing system and can achieve the power factor correction function in cooperation with a simple voltage booster circuitto effectively save cost; meanwhile, the method can obtain truer sampling data, guarantee the stable running of the system through the processing of the sampling triggering time.