With the wide use of I-section short, deep beams and wide flange beams, the section nonlinear effect of shear deformation on the bending normal stress becomes an important issue, because enormous calculation errors will occur by using the traditional beam theory in the design. With the bar simulation method, formulas are derived in this paper for the calculation of the bending normal stress with consideration of the shear effect and results are compared with those obtained by various analytical methods and the finite element numerical simulation results. The results indicate that when § is small or ø is large, the bending deflection is affected greatly by the transverse shear. Besides, compared with the existing analytical methods, the proposed method offers more accurate results with an extended scope of application, which can be used for the structural design.