Abstract: In this paper, an automatic bone maturation evaluation method based on "Chinese wrist bone maturation standard CHN" is studied, with emphasis on automatic edge detection in a hand X radiographic image and automatic bone maturation classification A knowledge based ASM（active shape model） with multiple masks and training sets is proposed and the effect of edge detection is improved Some formula of CHN is translated into digital features by combining shape and gray level information, and a hierarchical method is used in final automatic bone evaluation The experiments show that correctness and stability of bone maturation evaluation are improved