Abstract: For binary vein images,thi:paper presents a thinning algorithm based on maximal neighborhood point tracking (MNPT).The algorithm firstly estimates the width of the vein lines and figures out the neighborhood sum of pixels in the vein lines according to the width;then finds the discrete starting searching points;and finally gets the thinning vein image by tracking the maximal neighborhood point.Experiment results show that the vein skeleton extracted by the proposed thining algorithm has precise location,fine connectivity and smooth lines,so it is an effective thinning method for vein image.