Abstract: In order to establish the uniaxial compressive constitutive relation of hybrid fiber reinforced mortar (HyFRM) under the influence of high temperature and CaCO₃ whisker (CW), uniaxial compressive tests were carried out on steel-polyvinyl alcohol (PVA) HyFRM with different dosages of CW at six temperature levels of 25℃, 200℃, 400℃, 500℃, 800℃ and 900℃. The results show that with the introduction of steel-PVA hybrid fiber, the peak axial compressive stress of mortar is increased significantly. With the introduction of CW, the peak axial compressive stress of HyFRM is further increased before and after high temperature: Below 800℃, the peak axial compressive stress of 1.5vol%steel fiber+0.5vol%PVA fiber+2vol%CW is the best. With the increase of the high treatment temperature, the axial compressive stress-strain curve becomes flat from steep, and the peak axial compressive stress, elastic modulus and strain energy of HyFRM generally decrease. However, below 500℃, they decrease slowly and even increase, and the increases are most obvious when 1.5vol%steel fiber+0.5vol%PVA fiber+2vol%CW. At 800℃ and above, the compressive performance deteriorates sharply. A stress-strain damage constitutive model for HyFRM under compression considering the effects of high temperature treatment temperature and CW content was established. The damage constitutive model and damage variable can’t only preferably reflect the multi-scale fiber system in the different stages of uniaxial compression crack inhibition and retardation of mortar damage propagation, but also reflect the effect of high temperature on the initial damage of mortar. The observations by optical microscope and SEM reveal the influence mechanism of high temperature on the axial compression of HyFRM.