In order to study the mechanical properties of steel fiber reinforced concrete（SFRC），a new constitutive model of SFRC is established in this paper based on the smeared crack model of the plain concrete and considering the bonding effect between fiber and concrete. In this model，the reinforcement of the steel fiber is considered in two cases. Before the cracking，the steel fiber and concrete matrix are fully bonded，which meets the two-phase composite law. When the concrete crack initiates and propagates，the contribution of the concrete and the steel fiber is considered separately. And the strengthening effect of fiber on the concrete cracked plane is considered through the bond-slip model during the process of fiber partially debonded and fully debonded from the concrete matrix. Through Fortran programming，the proposed constitutive model is introduced into ABAQUS software by using the subroutine Umat，and the finite element model is established to simulate the tensile tests and 4-points flexural tests of SFRC. Though the comparison of numerical simulation results and available experimental data，the accuracy of the constitutive model is verified. Meanwhile，the mechanical properties of SFRC including tensile strength，residual strength，flexural strength，and toughness are analyzed in detail.