Abstract: FMSs are characterized by the ability to process multiple part types simultaneously.Theseparts compete for the finite resources in the system,this causes the occurrence of some undesired events suchas deadlocks. A petri net model,called colored resource-oriented petri net (colored POPN),is developed tothe resource contention process.This model describes the essential characteristics of the resource contentionin FMSs,so that it is possible to search the sufficient and necessary conditions for deadlock avoidance by using this model.