Abstract: Two efficient fieldbus protocol are studied, analyzeo and compared based on Timed Petri Net with procedures, in which transitions are described in high 1evel program Language. In the polling scheme, the producer/consumer communication model is used. Polling queues are managed by the master node. The polling request message is broadcasted to all nodes and the poll response message is broadcasted by the producer. In the token-passing scheme, the circulated token and the delegated token allow very different communication requires to be met respectively. They are managed by the arbitrator. Operations of two types of the fieldbus network models are simulated in the paper. The performances of response time, throughput and jitters are discussed in details. The differences of performances and the threshold of the response time with the limited jitters are given. The result show that: when the response time is greater than the threshold, the polling protocol in the fieldbus has a intrinsic rhythm and is very useful for the communication problems in continuous process control, the token passing protocol in the fieldbus just breaks the intrinsic rhythm and is better in discrete and hybrid process control.