Abstract: In order to reveal mechanical behavior of steel and recycled coarse aggregate concrete after high temperature， the recycled coarse aggregate replacement ratio of 100% recycled concrete cubic block and the artifactitious steel specimens were designed，which were put at normal temperature and at 200 ～ 800 ℃ ( differential varying by 100 ℃) to do mechanical tests of high temperature simulation fire． The appearance after high temperature of recycled coarse aggregate concrete and steel was observed，and the damage process，failure mode of recycled coarse aggregate concrete and yield strength and ultimate strength of steel were observed． The effect of high temperature on their residual strengths was analyzed and the formula to calculate their residual strengths was also proposed． The results showed that with the increasing of temperature，the yield strength of steel was in the change trend of decline after rising first． Temperature under 600 ℃ had little influence on ultimate strength，while the effect of temperature above 600 ℃ was significant． With the increasing of temperature，compressive strength decreased gradually．