In this paper, a GFRP-RPC composite beam bridge for double deck traffic is designed. The bridge is composed of two GFRP trusses and ribbed plates connected by glue bolts, and then the composite beam bridge is finally formed by pouring self compacting RPC concrete. In this paper, the scale model (1:8) of the composite beam bridge is studied by quasi-static loading test and finite element analysis under multiple conditions. The results show that: (1) After pouring RPC, the stiffness of the beam bridge is increased by 2.6 times, which indicates that the combination of GFRP and concrete is beneficial to the reasonable stress of the structure. When the lower part is loaded, the deformation of the beam bridge increases by about 10%, which is unfavorable to the structure; (2) after the RPC is poured, the chord stress conforms to the plane section assumption, and the stress of the composite structure is more reasonable; (3) the upper and lower chords are in compression bending and tension bending state respectively. When the upper and lower parts are loaded, the tensile stress of the lower chord is about 1.5 and 2.5 times of that of the upper chord, and the lower chord is weak; (4) the diagonal web member is in tension, and the straight web member is basically in compression. The loading mode of the upper and lower parts affects the stress form of the straight web member, and the design of the lower part bearing should consider the larger local tensile and compressive stress; (5) the concrete on the side of the roof is in compression, and the concrete on the side of the floor is in tension. The setting of web members is beneficial to the uniform stress of slab concrete.