In order to study the damage behavior of fiber reinforced concrete at high temperature, the acoustic characteristics of hybrid fiber reinforced concrete (PVA fiber and basalt fiber) at different temperatures were tested, and the mechanism was explained from the microscopic level by combining the results of the SEM. The results show that with the rising of temperature, the degree of ultrasonic waveform distortion is more significant, and the attenuation of waveform amplitude is gradually intensified; The incorporation of fiber or the increase of temperature will reduce the amplitude of the dominant frequency of the waveform and increase the energy dissipation caused by the ultrasonic penetration of the specimen. At high temperature, after PVA fiber is melted, a large number of pores remain and gradually form connecting pores, which promote the release of pore steam pressure and alleviate high-temperature damage, while basalt fiber continues to play a bridging effect to inhibit the continuous development of high-temperature cracks.