Abstract: The axial tensile mechanical properties of ultra-high performance concrete (UHPC) mixed with straight (short straight, long straight) and end-hooked steel fibers were studied through the uniaxial tensile test. Based on the test results, the effects of steel fiber content and mixed ratio on tensile strength, strain capacity and toughness of UHPC were analyzed. The results show that the multi-crack ductile failure occurs in UHPC specimens under axial tensile, and the inclination and bending degree of macro main cracks become more and more obvious with the mixing of end-hooked fibers. The axial tensile properties of UHPC with hybrid short straight and end-hooked steel fibers increase significantly with the increase of end-hooked fiber content, while the axial tensile properties of UHPC with hybrid long straight and end-hooked steel fibers show an opposite trend. Hybrid steel fibers exhibit the characteristics of staged, layered and interactive crack resistance and toughening during the UHPC tensile process. The UHPC with 1.0vol% short straight and 1.0vol% end-hooked steel fibers has the best axial tensile mechanical properties, and its tensile strength, strain capacity and toughness are improved by 28.2%, 147% and 31.1% respectively compared with the specimens with single short straight fibers. A uniaxial tensile constitutive model of UHPC with hybrid steel fibers considering fiber interaction and fiber reinforcement factor is proposed by analyzing the measured axial tensile stress-strain curves. The proposed model is in good agreement with the relevant test curves and can be used to predict the tensile stress-strain relationship of UHPC.