Abstract: As one of several important approaches of analysing discrete event dynamic systems(DEDS)Petri Net is used widely.In this paper we use a subclass of it—the timed event graph to analyse FMS,both in flow-shop type and job-shop type.The condition under which a sequence is feasible and the relationship between the number of pallets in the system and the productivity of the system are presented,and a quantitative analysis of main performance is given,including production period,flow time in the system and work in process,which provides a theoretical basis for the design and operation of the system.