Objective To investigate the characteristics of IOZ coating for passive containment after design basis accident, so as to provide data support to the design of passive containment. Methods The physical environment of test was designed refer to the working condition of the DBA:specimen in the thermostatic oven heated to 160 ℃ until temperature uniformity, then immersed in 20 ℃ water. After cooling to room temperature, the samples were immersed in 100 ℃ water for 60 minutes. The impact of DBA for coating was studied, and the main characteristics of the IOZ coating were thermal conductivity, dry film thickness, surface morphology, adhesion, etc. Results After the test, the DFT of the coating was 70 ~130 microns, the adhesion was 8. 5 ~13. 5 MPa, and thermal conductivity increases by 6. 8% , but the surface morphology was unchanged. Conclusion After DBA, the DFT, surface morphology and adhesion was unchanged, but the thermal conductivity was edge up.