The rationality of design resource reusable model is the key to judging whether a mass customization system has adequate flexibility and agility or not. Based on the demand of the Design for Mass Customization (DFMC), design resource reusable model should not only include high-level feature information such as demands, functions, principles and constraints, but also include the underlying structural information such as geometry features and assembly relationship. Function Surface is the media between the function and the structure in concept design progress, which is processed to solve the uncertainty when the function maps directly to the structure. Based on Function Surface theory, the multi-layer design resource reusable model including the entity product layer, entity module layer, shell part layer, Function Pattern layer and Function Surface layer is proposed. The designer can browse and find the reusable model based on the different position of the decoupling point of the customer order in the production process. According to the model and the statistical data of the management, the reuse rate curve of design resource is drawn, and the overall optimization method of the design resource reusable standard model and the evolution method of the core technology are proposed.