The coming national specification for steel highway bridge will adopt the design method of probability limit state based on the structure reliability theory. Then the statistical parameters of loads and resistance play a key role in this method. Based on the extensive survey and investigation on site, the parameters of resistance are calculated in the study. In the work, three aspects of resistance’s uncertainty which are the uncertainty of materials properties, geometric parameters of members and calculation model are analyzed respectively. Then, the statistical parameters of five typical members of two commonly used steels—Q235q and Q345qD—in steel highway bridges are calculated. The recommended statistical parameters of resistance of steel highway bridge can be a reference for the new specification.