In this paper, the authors study the query requirements of multimedia database and propose a structured multimedia object query language (MOQL). The language can support queries based on type, structure, synchronous relations, temporal relations, and contents of multimedia data. Taking the DB2 relational database system as a storage mechanism, they define a set of algebraic operators and some transformation rules, by which the MOQL queries defined by the users can be transformed into a set of algebraic formula and optimized. Finally, the algebraic formula can be transformed into execution plan in DB2SQL and C++ procedures, which can be run on DB2 system.