Abstract: In this paper,to address these issues,we propose an improved Canny algorithm based on traditional Canny algorithm.Firstly,we denoise smoothly by threshold function which is based on GCV criteria.Then we set high and low thresholds adaptively with Otsu after getting non -maximum suppression image.Finally,we refine the edge by using morphological structure element.Experiments show that our algorithm can get relatively ideal margin detection effects and avoid the shortages mentioned above,which will lay a good foundation for improving disease diagnose.