Applying intumescent coating system to steel members is one of the general methods to secure fire resistance performance of steel members. Intumescent coating system for fire resistance, however, has undesirable weaknesses that fire resistance performance of steel members is being deteriorated due to cracks and falling-offs of the coverings as time goes after completion of the coverings to the members. So Intumescent coating system whose use is increased has bigger durability alteration possibility by the environment than any other materials and it is necessary to understand changes of the durability and the fire resistance performance over a time elapse. This study is designed to understand changes in durability and fire resistance performance of intumescent coating system through follow-up tests on bond strength and unexposed surface temperature for the domestic intumescent coating system during two years.