Abstract: Objective To observe the clinical therapeutic effect and safety of ¹²⁵I radioactive seed implantation combined chemotherapy on colorectal cancer with postoperative liver metastasis. Methods A total of 52 colorectal cancer patients with postoperative liver metastasis were randomly divided into treatment and control group. Treatment group was treated with ¹²⁵I radioactive seed combined with FOLFIRI regimen(Irinotecan+5-Fu+LV) and control group was treated with FOLFIRI regimen. The clinical effi cacy and adverse reaction were compared between two groups. Results The response rate and median time to progression of treatment group were 74.1% and 15.6 months, and those of control group were 40.0% and 10.2 months, with signifi cantly statistical difference. The main adverse reactions, such as gastrointestinal reaction, liver function damage and myelosuppression at different levels, were found in both group, moreover, patients in treatment group suffered endurable pain and low-grade fever. Conclusion The clinical therapeutic effect of ¹²⁵I radioactive seed implantation combined with chemotherapy in colorectal cancer with postoperative liver metastasis is defi nite and adverse reactions are endurable.