A video segmentation algorithm for lower contrast between foreground and background based on Graph Cut and Sobel operator is proposed. Firstly the energy function containing color term and contrast term is constructed. Then the gradient of current frame and background image to adjust the gradient of the boundaries of current frame should be calculated,the color term and the contrast term of which can be imporoved by the result of sobel edge detection. Finally the energy function could be minimized by Graph Cut method and the segmentation result of the video could be got. Experiments shows the result in weak contrast situation is better than others.
