Abstract: This study aimed to investigate the improvement of tolance and pharmacodynamics of nano-micelle irinotecan formulation compared with irinotecan hydrochloride injection(Campto). The toxic effects of the two formulations on colorectal cancer cells COLO205, HT-29, HCT-8 and SW480 were tested in vitro. COLO205 tumor-bearing mouse model was constructed. The two preparations were given via tail vein injection to investigate the maximum tolerance dose(MTD)of tumor-bearing mice to the two preparations, and then to explore the improvement of anti-tumor efficacy of nano-micelle irinotecan formulation near the MTD. The results showed that there was no significant difference in the inhibitory effect of the two formulations on the four colorectal cancer cells in vitro. The MTD of nano-micelle irinotecan formulation and Campto was 432. 0 and 276. 5 mg/m² respectively. Both of the two formulations showed significant anti-tumor effect in vivo, and the relative tumor proliferation rate and tumor wet weight inhibition rate of nano-micelle irinotecan formulation at high dose(345. 6 mg/m²)were significantly better than those of Campto at two doses(177. 0 and 221. 2 mg/m²)(P< 0. 05).