To solve the problem of low shear capacity of existing voided slab bridges, the research proposed a strengthening method for improving shear capacity of existing voided slab bridge. Taking a voided slab girder of 10 m long as the research object, the finite element software ABAQUS was used to carry out numerical simulation on the voided slab and analyze influences of the thickness of the bridge deck overlay on improvement of shear capacity of the voided slab bridge. Analysis results show that the strengthening method of paving a bridge deck overlay can improve shear capacity of the voided slab and the shear capacity rises with the increment in the overlay thickness.