Abstract: The generalized conforming element for thin plate bending and the membrane element for plane stress were combined to obtain a plane shell element to analyze the shear lag effect for continuous skew box girder bridges. Comparison between experimental and computed results proved the effectiveness of this analytical method in the three-dimensional analysis of skew box girder bridges. As an example, skew box girders with different degrees of skew were analyzed respectively to investigate longitudinal and transversal distributions of shear lag effect under concentrated or uniform force, and were compared with the corresponding right box girders. The result shows that a skew box girder has more remarkable shear lag behavior than a right box girder. Shear lag effect must be fully considered in the design of a skew box girder.