Compared to normal strength concrete and high strength concrete, ultra high performance concrete (UHPC) with proper fiber friction has a denser micro-structure and higher strength. The dynamic mechanical properties of UHPC has gain more and more attention. However, the lack of dynamic direct tensile stress-strain model of UHPC lead to the distortion of the calculation results for blast resistance performance of UHPC components. To solve the existing limitations, dynamic direct tension tests were performed on UHPC using split Hopkinson tension bar (SHTB) apparatus. A total of 40 UHPC dynamic direct tension specimens including plain UHPC, steel fiber-reinforced UHPC with 1% and 2% volumetric fractions of steel fiber were characterized at high strain rate of 98-528 s^-1. The formulas for calculating the tensile strength dynamic increasing factor (DIF_ft) and the dynamic tensile energy absorption capacity (W_t) of steel fiber-reinforced UHPC at the strain rate of 10^-6~528 s^-1 were established. It is found that when the strain rate is at 133~296 s^-1, the dynamic compressive energy absorption capacity W_c of UHPC with 2% steel fiber content is 6 times of its dynamic tensile energy absorption capacity W_t. A method to determine the tensile breaking point of steel fiber-reinforced UHPC is proposed based on the total energy absorption equivalent principle between the measured dynamic tensile stress-strain curves and the established constitutive model. A tensile stress-strain model for steel fiber-reinforced UHPC considering dynamic toughness was established.