[Objective] The paper proposes a method to create new Ontology for reusable products based on the concept lattice theory, aiming to improve the traditional methodology. [Methods] First, we extracted classes, attributes and relationships data from product categories and made appropriate adjustments. Second, we created formal contexts and concept lattices to generate product Ontology automatically. [Results] The proposed method improved the product classification scheme and enhanced the reusability and sharing of Ontology. It also visualized the existing and potential entities as well as their relationships. [Limitations] Only used a segment of medical product Ontology to implement the proposed method, and then discussed its flexibility for eCl@ss product classification system. [Conclusions] The field and scope of Ontology need to be clearly defined before we construct product Ontology based on concept lattice. The categories should be sorted and grouped with scientific classification principles. We also need to build the property dictionary and define object properties. The Ontology will be generated automatically with formal context and concept lattice.