A study was conducted to specify the joint having greatest influence on drop jump (DJ) performance, and to investigate the factors involved in improving muscle output related to posture during DJ. Eight male athletes performed DJ from a height of 30 cm. The jumps were recorded using video cameras, and the ground reaction force was measured by a force plate simultaneously. There were significant correlations between DJ-index and mean joint power at the hip joint in Ecc. phase (r=0.725, p<0.05), mean joint power at the knee joint in Con. phase (r=0.730, p<0.05) and mean joint torque at the ankle joint in Con. phase (r=0.736, p<0.05), respectively. There was a significant correlation between mean joint power at the hip joint in Ecc. phase and mean joint torque at the ankle joint in Con. phase (r=0.912, p<0.001). At the instant of contact, higher activation of the biceps femoris group indicated significantly higher values for pelvic and pelvic-thigh angles than lower activation of the biceps femoris group. These results suggest that the function of the hip joint in Ecc. phase influences DJ performance and function of the ankle joint in Con. phase. Also, to improve the function of the biceps femoris in Ecc. phase, it is effective to incline the pelvis anteriorly at the instant of contact.