In the reconstruction and expansion projects of expressways, due to the increase in the vehicle load standards in the current highway bridge design codes, the reuse of in-service hollow slab beams urgently needs in-depth research. Therefore, considering the actual synergistic working effect of the hollow slab structure and the top surface pavement layer, a calculation method for the section stress of hollow slab beams considering the effective thickness of the concrete pavement surface layer is proposed. Taking the existing pre-tensioned prestressed hollow slab beam with a span of 10 m as the research object, the influence law of the effective thickness variation of the concrete surface layer on the stress at the lower edge of the hollow slab section under the increasing condition of automotive load standard is systematically analyzed. The results show that the increase of vehicle load in the standard will significantly increase the tensile stress at the lower edge of the mid-span section of the prestressed hollow slab beam by the pre-tensioning method. With the increase of the effective thickness of the concrete surface layer, the tensile stress at the lower edge of the prestressed hollow slab beam section by the pre-tensioning method shows a decreasing trend. Based on the above research results, further suggestions are put forward for the reuse of existing pre-tensioned prestressed hollow slab beam bridges in the reconstruction and expansion projects of expressways.