In this paper, we develop a queuing theory based analytical model to evaluate the performance of transactional memory. Based on the statistical characteristics observed on actual experiments, we model each transaction as a client requesting services from the computing system. Continuous time Markov chain is used to describe the start and completion (commit or abort) of the transactions. We analyze the mean transaction execution time to evaluate the performance of target transactional memory systems. Experimental results based on STAMP benchmarks show that our model can predict the performance of real transactional memory systems with an average error rate of 7.9%.