Abstract: Considering the problem that the traditional optical flow algorithm is a time-consuming computation. An integrated method of detecting human motion is proposed based on the sum of absolute differences (SAD) and optical flow. The motion sub-region is detected by the computation of SAD. The optical flow vectors of the object can be obtained by computing optical flow on the motion sub-region. In the post processing, closing and connected components analysis are used for the segmentation of human object. Experimental results showed the effectiveness and robustness of the proposed method.