Active Power Filter (APF) is a novel power electronic device, which can dynamically accomplish harmonic suppression and reactive compensation. The performance of APF is influenced greatly by the topologies, the harmonic current detection technique and the current tracking control method. To promote and develop the application of APF under high voltage and large capacity, the current researches about APF at home and abroad are reviewed, the topologies of APF are classified and sorted. At the same time, the harmonic current detection and current tracking methods of APF are summarized, and their advantages and disadvantages are comprehensively evaluated. Furthermore, the existing problems are described from the various perspectives. The research directions of APF’s techniques are prospected finally. This work is supported by Fund Program for the Scientific Activities of Selected Returned Overseas Professionals in Shanxi Province (2015).