Abstract: The relationships among peak compressive strain, cube compressive strength, elastic modulus, and axial compressive strength were established respectively based on 64 groups of Ultra High Performance Concrete (UHPC) compressive test data. The equivalent tensile strength of UHPC in the tensile zone was deduced through the mechanics of composite materials. Based on the plane section assumption, the formula for calculating normal-section flexural capacity of UHPC beams and the parameters of an equivalent rectangular stress block of UHPC in the compressive zone were deduced and the equivalent rectangular strength was calculated with the UHPC compressive constitutive relationship. Based on the data of 28 test beams, the feasibility of calculating the flexural capacity and the parameters of equivalent rectangular stress block was verified. The results show that the parameters of an equivalent rectangular stress block are reasonable and the calculated results of the normal-section flexural capacity of UHPC beams are in a good agreement with the experimental ones.