Abstract: Depending on the methods of literature, 3-D video analysis, interviews, mathematical statistics and logical analysis, the paper researches the techniques of the swinging legs in every phases, the correlation between the swinging leg techniques and performance in the process, the relationship between leg swinging techniques and boarding speed, the initial speed of body gravity at takeoff, the horizontal velocity of takeoff, the vertical component velocity and the take-off speed. The research results show that 1. there are some defects in China's top long jumpers in their leg swinging techniques; 2. The hip angle at the takeoff is small, leading to inactive forward and upward hip push; 3. The hip angle of the swinging leg is big while the swinging amplitude of the side hip points is small with slow speed; 4. The side hip of the winging leg significantly lags behind the front leg without being able to function as the leg on the part of the hip and the front swing of the swinging leg can not fit the take-off speed.; 5. In the buffer period, over emphasis is put on the the quick swing of the swinging leg without realizing the importance of hip points serving as an engine; 6. In the period of pedaling and extending, the take-off leg shows slow and small amplitude in hip push and insufficient pedaling, leading to the failure to gather all the power collected when taking off to maintain the same direction of hip push, pedaling and knee extending and to help the transfer of the body gravity from the lower to the upper body.

Key words: men, long jump, takeoff, swing, 3-D kinematics analysis