Objective: To investigate the effect of Tianzhicao capsule on tumor cell cycle. Method: S180 tumor-bearing mice were administraed with Tianzhicao capsule orally(0.5

1.0

2.0 g·kg-1

7 d). Cyclophaspharmide

the positive control

was given at a dose of 0.02 g·kg-1·d-1. The changes of tumor cell cycle after administration were detected by flow cytometer. Result: Tianzhicao capsule could blockade the course of tumor cell cycle. The rate of Sub-G1 and G0/G1 phase of Tianzhicao high dose group were increased from (2.26±0.11)% up to (2.61±0.04)% and from (47.34±0.70)% up to (55.23±1.05)% accordingly. And the rate of S phase was decreased. Conclusion: Tianzhicao capsule can arrest tumor cell cycle in G0/G1 phase and inhibit proliferation of tumor cell.