To consider the difference in the section rotation angle of the wing flange， web， and composite box girder when calculating the shear stress of a cantilever beam with variable section corrugated steel web， a displacement function was first established based on the rotation angles of the flanges， web， and composite box girder. The energy variational method was used to separate the shear contribution of the flange and web， and the bending moment equivalent was used to further separate the top and bottom flange shear. Secondly， the shear-stress solving program was established based on the stiffness matrix of the beam segment analysis element and the joint load array of the composite box girder with variable section corrugated steel web. Lastly， the study analyzed the shear stress and shear capacity ratio of the top flange， bottom flange， and steel web of the cantilever beam under various loading conditions. The results show that， when compared to the finite element calculation results， the accuracy of the calculation results of the shear capacity ratio of the top flange， web， and bottom flange after considering the difference of rotation angle can be improved by a maximum of 3.48%， 3.43%， and 6.91%， respectively， compared with the existing results of shear stress calculation of variable cross-section. The shear capacity ratio of each component of the cantilever beam depends on the load form. The values of the top flange and bottom flange reach the maximum under the concentrated load of the beam free-end， which is 12.82% of the free end and 60.81% of the fixed end， respectively， and the web shear capacity ratio reaches the maximum under the action of uniform load， which is 78.11% of the free end.