Strictly synchronized SPNs (stochastic Petri nets) are very popular in stochastic Petri nets made up of sub-models. Because of the problem of state space’s explosion, performance analysis of strictly synchronized SPNs has not been solved completely. Formulas that show performance equivalence of four elementary subnets, which are sequence subnet, parallel subnet, choice subnet and iteration subnet, are presented. A decomposition approach called STED (synchronous transition equivalent decomposition) is proposed in this paper and can be applied to SPNs with one or more synchronous transitions, especially such models with isomorphic sub-models.