In order to study the influence of the mechanical properties of the steel truss bridge in the rigid area, the 202 m simply supported through double-deck truss-arch system bridge is taken as the research object. Three finite element space models of joint hinged model, joint rigid model and rigid zone of joint are established. The influence of three kinds of joint rigidity on the internal force, combined stress and deflection of steel truss bridge is analyzed. The research shows that the rigidity of the joint has little effect on the axial force of the bar, but has a great influence on the shear force, bending moment and combined stress. The increase of the rigidity of the joint will cause the connecting bar to produce larger secondary bending moment and secondary stress. At the same time, the influence of joint rigidity on the deflection of member joints cannot be ignored. There-fore, in the design and construction of double-deck steel truss girder-arch system bridge, the influence of joint rigidity on the mechanical performance of the structure should be fully considered.