Active power filter(APF)is an important device to compensate harmonic and reactive current in power system and the key of the effective compensation lies in the real-time and accurate control．The paper analyzes some representative methods on single-phase APF, and introduces the principle, points out their demerits and merits. Around them constant control on inverter output voltage, one-cycle control, the active power filter based on the active power balance theory has a better development because they can hold the inverter output voltage a constant value and keep the THDi below 5%. The paper simulates the last method in the Matlab7.0, which the result shows is quite simple and performs good harmonics compensation.