The influence of degradation of shear surface asperity on the load transfer mechanism of the pile-rock interface in the shear process is studied. Firstly, the rough surface between concrete of the pile and bored stratum is abstracted as a series of identical isosceles triangles, and the size of a single rough body is defined by half-wavelength and dilatancy angle. Secondly, the Patton model is introduced to describe the relationship between macroscopic shear responses of the rough body and relative shear displacement. Considering the relative stiffness ratio between the hole wall stratum and the pile body concrete, based on the energy principle, a rough body degradation coefficient is introduced to define the behavior of the rough body surface wear and volume compression generated during the shearing process. Accordingly, the classic Patton model was then improved. On this basis, the vertical load transfer equation of cast-in-place piles considering the degradation of the hole wall roughness is derived. This equation can not only consider the influence of the shear surface roughness (half wave length and dilatancy angle) on the load transfer behavior of piles, but the physical meaning of parameters included in the solution is also clear. Finally, the finite difference method is used to solve the load transfer equation, which is compared and verified by engineering examples. The results show that the theoretical predictions in this paper are in good agreement with the field measured results, and have a certain reference value for the preliminary design of cast-in-place piles.