Based on the computer-aided system, the microstructure scanning electron microscope test and compressive strength test of high-performance concrete after high temperature are carried out to study the relationship between the microstructure of high-performance concrete and its macro-mechanical properties. The test results show that the changes in the microstructure of concrete are consistent with its macro-mechanical properties. As the temperature increases, the concrete aggregates gradually become looser, cracks gradually increase, crack widths become larger and inter-connected, and the macro-mechanical properties decrease accordingly. After the synthetic fibers are melted, they leave pores in the matrix that can reduce the internal vapor pressure of the concrete, thereby reducing the damage to the concrete caused by high temperature by 7.4%.