In current Chinese code for design of steel structures, the design values of all kinds of steel at mbient temperature have been listed, but there is no design value for steel at high temperature. In order to analyze the design values of steel under high temperature, 152 groups of mechanical properties of Q345 steel at high temperature were collected and the statistical parameters of material property uncertainties of Q345 steel under high temperature were obtained. The finite element model was established in the general finite element software ABAQUS to calculate the ultimate loading capacity of 360 groups of Q345 steel axial loading member under high temperature and the statistical parameters of model uncertainties of Q345 steel axial loading member under high temperature were generated. The partial factors for resistance of Q345 steel under high temperature were proposed by using the first-order second-moment reliability method which was programmed through Matlab and the reliability of the proposed resistance partial factors were checked. The result meets the reliability requirement of building in fire and have sufficient reliability.