A different type of load draws non-sinusoidal current from the mains, degrading the power quality by causing harmonic distortion. These nonlinear loads appear to be prime sources of harmonic distortion in a power system. In addition, the harmonic currents produced by nonlinear loads can interact adversely with a wide range of power system equipment, most notably capacitors, transformers and motors, causing additional losses, overheating and overloading and interferences. The aim of this paper is to review an active power filter that commonly used to mitigate harmonics. Thus, to solve this harmonics problems The system is verified by simulation using Matlab/Simulink simulation package. The paper starts with a brief overview of harmonic distortion problems and their impacts on electric power quality, how the active power filter mitigate this problems and the verifying using Matlab software. The proposed filter minimizes the harmonic distortion is within an acceptable range