An improved frame difference method on the basis of Kirsch edge detection and background difference is present ed,which is designed for dealing with the overlapped parts and the incomplete object contours in moving objects detection with the conventional fr ame difference.Firstly,the difference of three consecutive frames is used to obtain motion regions,and then the bound ary of current frame is defined by Kirsch edge detection.Finally,the complete mo ving object forms through using motion regions and edge detection for calculatio n with or logic operator.The background difference is applie d to extract objects and eliminate noises.The experiment results prove that the target regions detected by this method are more complete and can effectively avoid the phenomena of “missed” and “false alarm”. Compared with some other algorithms,the proposed method has better performance.