The purpose of this study was to investigate the kinematic factors influencing: 1) the Leg Beat Action during Giant Swing Backward in Horizontal Bar and 2) the Dismount of Double Salto Backward Stretched with 720° Turns. A comparison has been made between international top class (Subject 1) and national level (Subject2) gymnasts in order to get insights into the technical conditions and the develop directions of our national gymnast. 3D kinematic data were collected during final competition of horizontal bar in 1997 International China Motor Cup Gymnastics Meeting by using Peak Performance 3D Motion Analysis System (60Hz). The Giant Swing Backward in horizontal bar was divided in to 6 positions and 5 phases and the Dismount of Double Salto Backward the 720° Turns was divided in to 4 positions. The 12-segments human body model war adopted and 17 landmarks were digitized to conduct kinematic analysis. The movement was divided into two parts: the Giant Swing Leg Beat Action on the bar and the followed dismount of Double Salto Backward Stretched with 720° Turns. After analyzing and comparison, the results were as follow: 1. The Giant Swing Leg Beat Action on the bar (1) The movements performed by international top class gymnast (S1) and national level gymnast (S2) during first phase (from handstand position to hang-up position at vertical line in first circle) were similar. The shoulder and hip angle as well as the radius of c.g. circling the bar of S1 is smaller than that of S2. (2) At position4 (270° from handstand position), the angle of shoulder and hip of S1 subject is changing from flexion to extension rapidly. After position 5, by closing the distance of should and hip, S1 showed significant shorter rotation radius of c.g. around the bar and speeded up the speed of circling. S2 did not use the changes of joint angle to conduct the technique of leg beat action. His movement is only like that of ordinary Giant Swing. (3) The major difference between S1 and S2 is the movement performed during the movement process of position3, 4 and 5. S1 was well prepared to adopt body-straightening, back-bowing, shoulder-sinking and leg beat action. Unfortunately, S2 did not present those skills and failed to show the rhythm of beat action. 2.The Dismount of Double Salto Backward Stretched with 720° turns. (1) At the instant of leaving off the bar, the angles of shoulder and hip of S1 are 107°, 131° respectively. They are smaller than that of S2 which are 132° and 173°. Besides, the height of c.g. and angle of trunk of S1 are 2.68 m and 81° respectively, they are higher than that of S2. It indicates that , at the instant of leaving he bar, S1 flexed his shoulder and hip to curve his body while he was releasing the bar. (2) The maximal flight height of S1 is 3.88m, and that of S2 is 3.7m. It shows that S1 get higher amplitude after he left off the bar and get longer flight time to perform the double salto backward with 720° turning body. (3) At position 4, S1 had completed his double salto backward Stretched with 720° turn and was prepared well for landing. The angle of S2 between the trunk and Horizontal plane is 77° at the position 4 by flexing the hip. He did not land with straighten body.