Achilles tendon determines the downward movement of ankle joint. If the Achilles tendon is thicker, the ankle joint movement can be better controlled. Achilles tendon is a tendinous structure that migrates from the lower part of calf triceps, namely gastrocnemius and soleus, and ends at calcaneal tubercle. It is one of the thickest and largest tendons in the human body, which is of great significance for walking, standing and maintaining balance. Traditionally, under the same conditions, people with longer achilles tendon, that is, people with larger values of (fibula tendon length/calf length) × 100, have relatively strong running and jumping ability. People often exaggerate the correlation between the length of "Achilles tendon" (actually gastrocnemius tendon) and jumping ability according to the case of NBA black athletes, and even think that the length of "Achilles tendon" determines jumping ability. Many recent research results show that the two indexes of gastrocnemius tendon length/calf length/achilles tendon length/calf length have nothing to do with jumping ability, which is inconsistent with the traditional view. The possible reason is that tendon is a kind of biomaterial with high strength and low deformation. In the process of exercise, it does not provide power by itself, but is pulled by muscles to produce exercise, and its exercise ability is related to the size of muscle tension. Therefore, the traditional Achilles tendon measurement method needs to be improved in material selection.