Considering the shear deformation effect of piles, the calculating theory of m method assumption for piles was presented by using the single generalized displacement theory of deep beam. The initial parameter formulae to horizontal displacement, slope, moment and shear force were derived. The unified non-dimensional functions were also put forward. According to the boundary conditions, the initial parameters solutions were determined. The changing figures of non-dimensional functions with converting length and ratio of bend stiffness to shear stiffness were plotted. Some conclusions were summarized that when the converting length was less than 3.0, there was little influence of the ratio of bending stiffness to shear stiffness on the non-dimensional functions, while the converting length was greater than 3.0, the influence of the ratio of bending stiffness to shear stiffness on the non-dimensional functions became obvious; the influencing degree of the shear deformation effect was related to the boundary conditions. Example results showed that shear deformation can enlarge the horizontal displacement at the top, lift the position of zero moment, change moment distribution and magnify the soil pressure on pile.