This paper proposes a moving target detection algorithm based on single Gaussian background model.The algorithm uses four frame difference method to determine the movement target area at first，and background model is updated by single Gaussian.Finally moving the shadow by （r，g，I）feature space.So the moving object is extracted.Experiment results show that the algorithm can update in real-time the background in changing scene and detect the moving object quickly.The calculation is simple and robust.This algorithm works well in the laboratory test and field application.