Abstract: The coating of AP1000 nuclear island steel containment vessel undertakes the safety function; its heat transfer performance significantly affects the function of the passive containment cooling system, and must meet the minimum safety requirement during the entire lifetime. The salt fog accelerated aging test was carried out to study the aging mechanism as well as the relationship between thermal performance and aging. The test result shows that with aging zinc powder in the coating changes into zinc salt, while the change of indicators such as coating wettability, specific heat capacity and emissivity contribute to a higher heat transfer performance of coating. The heat conductivity indicator of coating shows a gradually decreasing trend in the process of salt fog aging, imposing an unfavorable effect on the heat transfer performance of coating. However, after 3500 h salt fog aging test, the heat conductivity of coating tends to be stable, meeting the minimum requirement of the safety analysis.