In order to improve the range-measuring accuracy in stereo vision,a sub-pixel parallax is needed.The Mutual Information (MI) theory is combined with multi-resolution method to realize the goal of sub-pixel point matching.Firstly,Bouguet algorithm is used to rectify the left and right images making their epipolar line forward-paralled.Then Harris corner detector is brought to find a most characteristic corner as candidate matching point.After that,Most Cross Correlation matching rule is introduced to search the matching point.The 20×20 areas whose center is the left and right matching point are magnified by 10 and 100 times respectively.The low-resolution image is registered with MI theory,followed by the seeking of higher precision in the high-resolution image.Finally,combined with the integer-grade parallax,we can get the sub-pixel parallax.The experimental result shows that the method used in this article can improve the precision to 0.01 pixel level.