As the dynamic range of the targets in X-ray images of feet is wide, and the overlapping interval of the background gray value and the target is large, this article comes up with a bone-image segmentation method in X-ray pictures of feet. First of all, composite enhancement will be applied, then the distribution features of target will be exploited to carry out a dynamic partition, finally density function will be incorporated to make the segmentation. The experiment has proved that this method can effectively separate the bone image of feet.