It is very important to analyse the performance of the asynchronous pipeline during the design of the asynchronous circuit. But there is no very efficient way to evaluate the performance of the complex nonlinear asynchronous pipeline. The queuing network is a very intuitive tool to model the asynchronous pipeline, and a performance model of the asynchronous pipeline based on the forkjoin queuing network with blocks has been introduced in this paper, then an equivalent stochastic marked graph has also been introduced, and the upper and lower bounds of the average cycle time are presented in the end of this paper.