As most of the Computer Aided Tolerancing tools can only deal with the CAD models with an ideal surface and can not reflect manufacturing errors in physics and geometry, this paper explores a multi-scale representation method for skin model shapes in the Geometrical Product Specification. A discrete data modeling method was proposed for the simulation of topographic errors of surfaces and section profiles of a product in macroscopic and microcosmic scales based on new-generation geometrical product specification. Firstly, a simulation method for multi-scale surface topographic errors based on discrete wavelet was presented. Then, discrete wavelet was used to simulate multi-scale surface topography errors for sampling data of the surfaces and section profiles of a part. Finally, multi-scale surface topography errors were composed and skin models for two-dimentional profile and three-dimentional surface were acquired. The simulation and experiment results show that the proposed method represents skin models with multi-scale surface topographic errors and the average relevant error between the results of Ra obtained by a white-light interferometer and the proposed simulation method is less than 4%. The results verify the correctness and applicability of the proposed method, and provide a valid way for more comprehensive representation of skin model in new-generation geometrical product specification.