Moving object detection is one of the challenging problems in video monitoring systems, especially when the illumination changes and shadow exists. A method for real-time moving object detection is described. Anew background model is proposed to handle the illumination varition problem. With optical flow technology and background subtraction, a moving object is extracted quickly and accurately. An effective shadow elimination algorithm based on color features is used to refine the moving objects. Experimental results demonstrate that the proposed method can update the background exactly and quickly along with the varition ofillumination, and the shadow can be eliminated effectively. The proposed algorithm is a real-time one which the foundation for further object recognition and understanding of video monitoring systems.