In order to investigate the effect of insulin-like growth factor-1 (IGF-1 on the cyclic change of tendon cell, the 6th generation of cultured tendon cell were selected, and 20 ng/ml IGF-1 was added to the medium. After 48 hours, the cells were determined by flow cytometer, as well as the control cells. The results showed that the time of G1 phase, DNA synthesis phase and G2M phase in IGF-1 group were 11.8 hours, 21.4 hours and 6.8 hours respectively, while those were 25.6 hours 22.6 hours and 21.8 hours respectively in the control group. It was showed that the time needed for G1 phase and G2M phase was shortened by IGF-1.