An analytic model for Prioritized token ring is presented in this paper. Its protocol is based on prioritized token ring with reservm-on (R-PTR). Since the protocol of the R-PTR is simple and the performance of the R-PTR is not inferior to that of the IEEE standard 8025 (IEEE-PTR) under almost all tr&c load environments, we use the R-PTR as our token ring model. By using the properries of Markovian process, the expressions for average throughput and average packet transmission delay are &rived. The results obtained from the annlytic mo&l are compared with that of the simulation model.