Aiming at the evolution problem of core module in product family design, the module evolution law and process evaluation were analyzed. A method for law analysis and evaluation in the module evolution was proposed. The relationship between customer demand and module design was also studied. The core module standardization and universal indicators based on existing products were analyzed. An analytical model for core module evolution was established in the process of needs analysis, and the model was trained by the history data. The changing law of design and craft was obtained by demand evidence reasoning in core module. Based on the evolution law analysis, the design parameter and reuse degree were also analyzed for core parts. Comprehensive evaluation value for core module evolution was gained. Finally, the effectiveness and feasibility of the method was tested by core module design of small wheel loaders.