Abstract: In view of problem that conventional PID controller is difficult to obtain satisfactory control effect due to sampling frequency and other factors, a control strategy of fractional order calculus for shunt active power filter using improved Oustaloup algorithm for solving fractional calculus was studied. The Matlab simulation results show that the control strategy can better stabilize DC side voltage to set point, and can get smoother grid current which is closer to sine wave than conventional PID control strategy. Impact current at the compensation instant is small, and tracking and compensation current can track command current effectively.