BOM(Bill of Materials) is a list or description of raw materials, parts and assemblies that define a product. Although it is very important for maintenance information system of urban transit, it has problems that the size of database, inaccuracy and the flexibility which is measured as the number of updating records in accordance with added new product or engineering change. To solve these, we divide BOM to a master BOM and various function BOM constructed from the master BOM. That is the component based BOM management system, which is mutually independent and integrated efficiently using component technology. Consequently, after defining the component based master BOM, it is easy to manage the data structure, even restruct, in case there is a need for change of environment or data.