The characteristics of assembly process in equipment industries are analyzed, which are discrete manufacture, complex production, complex supply chain, much customized production than traditional manufacture enterprise. The material flow model of assembly process is proposed based on discrete event simulation. This paper studies the restriction condition and correlation of material flow in assembly process, and designs the material flow simulation system of equipment industries. The simulation model is applied to the numeric analysis of an equipment manufacture enterprise. The important complication of material flow is analyzed, and the advice of material flow process optimization is given.