Service is means of the first round attack in a volleyball game, as is an aggressive skill of taking immediate advantage and gaining direct points. Since FIVB modified the rules to Rally point system is 1999, whether the game is won or not has almost depended on how many points the team can get when serving. Therefore, the aggression and precision of service appear more important than before. This study, based on mechanics, tries to make a quantitative analysis of the elements that affect jump service as a proof of investigation and evaluation for coaches' reference on future training and instruction. This study takes a male volleyball player Yeou-yu Chen of National Taiwan Normal University, as an subject by filing and analyzing the film of his jump service movement with a Panasonic AG-450 high-speed video camera at the speed of 60 fields per second. The results digitalized by Peak performance System are listed as follows 1. During the approach; the distance of approach is 2.98m. The three step spans are distributed as the first step shorter than the second, and the second shorter than the third; that is, 0.54m, 0.97m, 1.47m. The last approach velocity is 3.88m/sec. The angle between lower limbs and the court at touchdown is 68.71 degrees, which advantages to accelerate during the approach. 2. During the take-off when the player crouches, the angle of his knee joints in 113.89 degrees, the angle of take-off is 62.71 degrees. The resultant velocity of the subject's scenter of gravity at take-off is 3.96m/sec. The horizontal distance from the take-off point to the end line of the court is 0.21m. 3. In the air; the horizontal displacement of the subject center of graveity is 0.74m; the vertical displacement of the subject's center of gravity is 0.78m; the altitude of the ball hitting point is 3.03m.