Reliability, mobility and operability of the motion image’s analysis system have a major impact on the research and analysis of sports techniques. In this paper, it take the national secondary level sprinter as the study object, designs human body joints’ automatic identification system for sprinter, analyzes the body contour for sprinters, by studying the analysis algorithm is simple and scientific, gives the tracking area of human body contour in the motion process, provides the measurement methods of the study object and the mathematical model of the joint points extraction, obtains the discrimination model and processing methods on the special circumstances as the joints of the visible side into the body contour lines, the blocking of the joints in the invisible side and the effects of hand on the hip joint determination, and provides a scientific basis for the motion analysis and sprint technical improvements.