Abstract: Modelling and managing of complicate objects is vital to the engineering database management system. This paper discusses the modelling and operation of complicated objects based on relation in CIMS/EDBMS which has been developed successfully. Complicated objects are aggregated by relevant tuples of some relation tables. Inserting, deleting or querying a composite object means inserting, deleting or querying the relevant data of the complicated object and its components in attribute tables, method tables and relation tables.