An automatic human motion tracking algorithm combining improved Snake model and optical flow was proposed. The initial contour most close to human body was acquired by corner detection thus decreasing the iterations,and the probability of converging at local extreme value of Snake model was reduced. To resolve the problem that the tracking with Snake model is unstable and often loses the object,the strong feature points were chosen from the contour points in current frame for optical flow estimation,and then the result was chosen as the initial contour of next frame. Experimental results show that improved Snake model can make the initial coutour deform to the actual contour of human body,and realized the automatic and real-time human tracking.