The rapidly growing interest in building up multimedia applications has created a need for applying database technology to multimedia systems, to support the efficient access, query, and retrieval of complex multimedia information. In this paper, an Object Relational Multimedia Data Model (ORMD) has been proposed for modeling of multimedia objects. The ORMD model supports not only various relationships but also the hyper links among the multimedia objects. Therefore, querying and navigating of multimedia objects can be facilitated. Based on this data model, an infrastructure design of multimedia database system has been presented. Multimedia extensions of data types and query language have been designed to facilitate various queries of multimedia objects. Currently, we are implementing a prototype, called Multimedia Information Retrieval System to support the efficient querying and navigating of multimedia objects. The development of MIR System shows the potential of features of extending it to diverse multimedia applications, such as digital libraries, Internet video server etc.