The movement of vacated swing 720°followed by horse stance landing was measured by 3 D imaging to obtaine the relevant motion characteristic parameters of different stages. From the perspective of biomechanics, the influence factors of knee injuries during the landing stage were discussed. The results show that the knee injury induced by the movement vacated swing 720°followed by horse stance landing is common, and the main injuries are meniscus injury, lateral collateral ligament injury, and crucial ligament injury. The impulse force generated by landing is the key factor of knee joint injury, and the influencing factors of the impulse forces are athlete's weight, flight height, and landing type. Weight is relatively stable, and flight height determines the quality of the movement. Higher flight gains higher quality of the movement and longer time of landing. If the weight and flight height are stable, athlete can adjust the body movement to change the moment of inertia and two knee angles in landing phase for prolonging the landing time and lowering the peak value of landing impulse force, which could be reasonable for protecting knee joint.