To meet both the needs of reusability and semantic interoperability of limits and fits knowledge and the needs of limits and fits data access performance, the tier structure of shared concepts and data storage is introduced to organize the limits and fits knowledge. Considering the limits and fits ontology as the shared concepts, we manage the limits and fits data with relational database management system and express the relationship between the data and the concepts by mappings. Then the limits and fits data can be accessed through the limits and fits ontology. In this way, the needs of limits and fits knowledge reusability and semantic interoperability are met, while ensuring the efficiency of limits and fits data access. The feasibility and effectiveness of ontology based limits and fits data access are demonstrated by a prototype system and a practical example.