There is still no proper method to measure the loading on legs of an animal.Walking trace analysis is used as a quantitative method in this study. Ten rats having their left calcaneal tendons transected were used. The feet of rats were dipped in the developing fluid, and let them crawl over the film to get the foot prints. The foot prints were then measured to evaluate the loading of the hind legs. The results showed that the foot prints of the operated left hind legs were smaller than the opposite ones. The rate of the foot print area of the two sides(Sr) was calculated and showed siguificant difference(P<0.01) for a rather long period and gradually approaching the value 1, as the operated leg healed up as time goes on. Hence we conclude that walking trace analysis can evaluate the loading of animal leg representing the actual condition.