This study investigates the effect of high temperature on microstructure and mechanical properties of high-toughness fiber-reinforced cementitious composites. Pore size distribution, microstructure, and mechanical properties are tested after exposure to 20, 200, 400, 600, and 800°C. The variation of chemical compositions after elevated temperatures leads to color changes of fibers and matrix, which can be clearly verified from energy dispersive X-ray analysis (EDAX). Furthermore, pore size of the composites decreases gradually at 200 and 400°C. Compressive strength varies consistently with the microstructure, showing that fire damage does not inevitably lead to the deterioration of mechanical properties. However, residual flexural properties decrease significantly because of the melting of PVA fiber. As a covering layer of the structures, the composites exhibits excellent fire protection to reinforced concrete columns.