In this paper, a mapping model for product surface morphology design based on ergonomics is proposed. The method advances the traditional approaches based on anthropometric measurements to a new one based on digitised product surfaces; thus, it simplifies the complexity of non-uniform rational B-spline surface representation during product design. The method was constructed by converting the experimental data to the surface shapes based on the pressure distribution map. An adjustment algorithm is presented to eliminate the errors in mapping non-planar base shapes. The experimental mapping data are pretreated, so that the mapping process reflects the statistical characteristics of the tested groups as far as possible. Based on the mapping model, a prototype implementation system for ergonomic product design is developed. As an example, a car seat design is presented to show the performance and availability of the method.