Abstract: This paper presents a new optical flow computation method based on HS constraint and outline condition for the discrete region of both gray change and velocity flow in video image.Firstly,a Gaussian filter is used to smooth the image so as to reduce noise.Secondly,an improved Horn-Schunck method is used to calculate spatiotemporal gradient,and the velocity of optical flow is calculated on the basis of combining the two constraints.Simulation results show that the method can calculate optical flow in discontinuous regions and is robust.