Abstract: A warping displacement function and a shear rotation are introduced in a longitudinal displacement function for considering the shear lag effect of a box girder and the shear deformation of corrugated webs. Based on a variational principle, an analytical method for calculating the deflection of corrugated box girders is proposed. For the cases of single-box single-cell and single-box double-cell girders, the results of the proposed method are compared with those of the methods which only considers the effect of shear deformation of corrugated webs and those of the finite element methods. The results show that the proposed method has high accuracy. The shear deformation coefficient significantly increases with the increase of depth-span ratio and width-span ratio while the shear lag effect coefficient is less affected by depth-span ratio.