In order to improve the performance of current tracking algorithm of traditional space vector pulse width modulation（SVPWM）， an optimized method for shunt active power filter（APF） is proposed. The optimized current tracking algorithm uses the phase-to-phase current error to decide the district of space instruction voltage vector. Compared with the traditional current tracking algorithm， detection of three-phase network voltage and the complex calculation for deciding the scope of space instruction voltage vector are not needed. This significantly simplifies hardware circuit and its related algorithm design. The two algorithms for current tracking in an APF are validated through a simulation experiment with a circuit model that contains a three-phase uncontrollable rectification RL load.