In order to satisfy the demand of the double-deck traffic in city, a concrete box girder model with rectangular web openings was designed with ratio of 1:6. Experimental study was carried out to investigate the flexural capacity of the model girder with double uniformly distributed load. The finite element model was established based on the experiment and the results agreed with measurement results. The effect of the web openings on the girder was explored. The results demonstrated that the deflection caused by load on bottom plate of box girder was 9.7% more than that of load on the top plate. The deflection of girder with web opening is 22.9%~28.1% greater than that of girder without web opening. Compared with girder without web opening, the shear lag of girder with web opening increased, of which the maximum value was 62.0% in various working conditions. simply-supported concrete box girder with web openings under double uniformly distributed load affect the flexural capacity.