In this paper, we present methods of translating transactions from object-oriented database(OODB) to relational database(RDB). The process involves schema mapping in data definition language(DDL) and transaction translation in data manipulation language(DML). They include scheme definition, data query and transaction operation of insert, update, and deletion. We also discuss the object-oriented features in OODB operations that are not supported by RDB, such as class hierarchy, class composition hierarchy, and set attribute, and provide a general solution to realize those mechanisms by traditional relation operations. The result of the transaction translation can be applied into adding object oriented interface into relational database management system (RDBMS) and to the interoperability between OODB and RDB.