To study the effect of the new cementitious composite material named UHPC on the force of the combined bridge deck, the differences in structural stress, vertical deformation, and fatigue performance between the UHPC combined bridge deck and the traditional steel bridge deck are compared by finite element analysis with the background of the actual project. The results show that the UHPC material can significantly improve the stress performance of the combined bridge deck panels by its better mechanical properties. Compared with the traditional steel bridge panels, the UHPC combined bridge deck can effectively reduce the tensile stress of steel bridge panels by about 43.2%~69.6%, and improve the vertical stiffness of the bridge deck by 1.2~1.4 times. Improving the local fatigue performance of the steel bridge deck also has a more significant effect and a very good application prospect.