This paper presents a multimedia data presentation model-actor model,which is built over the conceptual model of multimedia database.This model applies place -duration Petri net to describe the temporal relationships among multimedia objects,and introduces the stage expressions associated with transitions to describe the spatial relationships among multimedia objects,so as to model the spatio-temporal composition of multimedia data.The formal abstraction model and implementation model are defined.The presentation algorithm of multimedia object is presented. The query model of multimedia database is proposed.