Abstract: Using Polyisocyanate as cross linking agent， preparation of ¹²⁵I radioactive covered metal stent with polyurethane. The dipping times, solution concentration of polyurethane and time of dipping on the coating thickness were studied. The membrane thickness was 7.9 μm. The specimens from 30 days after the experiments were collected and the radioactive material leakage rate was detected by physiologic saline immersing test. The ¹²⁵I radioactive material leakage rate in saline was 2.13%. Specifically, using Polyisocyanate as cross linking agent reduced more of the radioactive material leakage rate. The adhesive force between the coating layer and matrix was studied. After expansion three times, the membrane kept no cracks, tear, tilt and other defects. The polyurethane membrane on metallic stent which was covered by dipcoating technique could decrease the ¹²⁵I radioactive material leakage in saline，and the distribution of the radioactive material in such a membrane was quite homogeneous.