Abstract: This paper proposed the simplified calculation scheme for analysis of transverse internal forces of single-cell box girder, and made out the numerical computer PC-1500 program using finit stripe method. Combined with the several box cross-sectional dimensions and National Load Standard of Highway Bridge Norm, the analysis was completed in detail. Based on the work, the author presented the additional recommendable formulas with respect to effective width of load-distribution, which may be used as a reference for design and modification of highway bridge norm.