A piecewise reaching law variable structure current compensation control strategy was designed base on modeling and analyzing the three phase shunt active power filters to suppress the influence of the compensated effectiveness generated by parametric variations. The simulation and experiment results show that the proposed variable structure control strategy was insensitively to system disturbance, had good robustness and could effectively eliminate the chattering problem existing in traditional exponential reaching law variable structure control. The dynamic response speed of the system was fast, the power grid current was sine wave and as the same phase as the voltage, the THD of the current was low and the compensation effect was obviously better than that of the traditional current hysteresis-band tracking control strategy.