The high temperature caused by fire will cause serious damage to cement-based composites, and mixing basalt fiber can improve the high temperature resistance of cement-based composites to some extent. In order to study the performance changes of cement mortar mixed with different kinds of basalt fiber and polypropylene fiber after high temperature, the basic mechanical properties of blended fiber cement mortar after high temperature were tested, and the microstructure of blended fiber cement mortar was analyzed by means of scanning electron microscope (SEM) and mercury intrusion test. The results show that the mixture of different types of basalt fiber and polypropylene fiber can improve the high temperature resistance of cement mortar. When the temperature is 200 ℃, due to the secondary hydration in the cement mortar, the compressive strength and flexural strength of blended fiber cement mortar are significantly improved. As the temperature rises to 800 ℃, the internal structure of cement mortar is destroyed, the porosity gradually increases, and the mechanical properties gradually decline. However, the performance of blended fiber cement mortar is still higher than that of the reference group, because the polypropylene fiber leaves a large number of pores after melting at high temperature, alleviating the internal pore pressure of cement mortar, and the basalt fiber plays a bridging role in cement mortar, and the propagation of high temperature cracks is alleviated.