This paper aims to meet the increasingly diversified and personalized market demand of mechanical and electrical products, and improve the stability of product module division and the reliability of modular scheme evaluation, an integrated method for modular division and evaluation was proposed. The paper analyzed the function and structure of the product, a quantitative information model of the product was built up. The weight of each quantitative index was distributed reasonably and comprehensive matrixes describing the relationship between components were constructed. The clustering algorithm based on atomic theory was used for module division. By changing the module granularity, several feasible schemes for product module division were obtained stably. In order to construct a comprehensive evaluation model of modular scheme to determine the optimal module division result, the modular degree of products and the module complexity based on information entropy were considered. The modular design of a small engraving machine was carried out by using the integrated design method of module division and comprehensive evaluation. Furthermore, by comparing the modular results obtained by atomic clustering algorithm and other module division methods, the feasibility and efficiency of the proposed design method were verified.