Abstract: Twenty inpatients suffered from malignant tumors with twenty-four lesions were treated with ¹²⁵I permanent brachytherapy seed in Peking University Shenzhen Hospital, and the feasibility, curative effect and adverse effect of the treatment were observed. Before ¹²⁵I seeds implantation, the threedimensional treatment planning was preconcerted. There were two methods to implant ¹²⁵I seeds. One was to insert the seeds in the location of residual focus and metastatic lesions of the tumors directly in ordinary operations or through laparoscopy under general anesthesia. The other was to implant the seeds into the tumors through percutaneous needles by the guidance of CT scanning or color doppler ultrasonography under local anesthesia. The implantations for all of the 20 patients (24 lesions) were performed successfully. During and one week after the implantation, the distributions of the planted seeds were approximately the same as the scheduled three-dimensional treatment planning, and no seed migration was found. Adverse reactions during and after the operation were slight and recovered after correlative treatments. Clinical symptoms were palliated and serum tumor marker decreased to a different extent among most patients. The complete remission (CR) rate is 20.00％ ( 4/20 patients )，the partial remission(PR) rate is 35.00％ ( 7/20 patients)，the stable disease (SD) rate is 30.00％ ( 6/20 patients ), the progressive disease (PD) rate is 15.00％ (3/20 patients), and the overall response rate (CR+PR) is 53.33％ ( 8 patients). ¹²⁵I seeds implantation for targeted therapy is convenient, safe and effective on malignant tumor, and is well worth advanced application.