Abstract: Hysteresis current controllers with fixed band for active power filters (APFs) have limited compensation ability, so a new one with variable band based on fuzzy rules was proposed. Modeling the APF and analyzing the principle of hysteresis current control revealed that the compensation ability to harmonic current is closely related to the width of the hysteresis loop. In the fuzzy control rules, the deviation and its changing rate of actual current from instruction current are input variables and the hysteresis loop width is output one. The hysteresis loop width can be regulated by fuzzy control based on the compensation requirements. PSIM simulation results show that the ability of APF to track harmonic current is improved by the method, especially when harmonic current comes through the zero and vertex points. Experiments verify the practicability of this method on eliminating harmonics.