Objective:To evaluate the efficacy and toxicity of Irirotecan(CPT-11) combined with 5-FU/CF in the treatment of metastatic colorectal cancer, in which FOLFOX4 or LV5FU2 had failed to cure it. Method: 46 cases of metastatic colorectal cancer patients were treated by CPT-11 combined with 5-FU/CF for one cycle every two weeks; namely, CPT-11 was given by 180mg/m2 iv d1, CF by 200mg/m2 iv d1-2, 5-FU by 400mg iv bolus d1, and 5-FU by 600mg/m2 iv 22h d1-2. Two weeks was a cycle. The study term was 3-6 months. Result:CR was 0, PR was 39. 13% (18/46) , SD was 43.47% (20/46) , PD was 17.39% (8/46) and CBR was 82.69% (38/46). The clinical reaction evaluation efficiency was 78. 86% (36/46). Their life quality was notably improved. Conclusion:CPT-11 combined 5-Fu/CF can be used as second-line treatment for metastatic colotedal cancer.