Abstract: With growing awareness of the flexible workflow, reliability of flexible workflow system has become more and more important, as one of the main reasons of the impact of work flexible workflow, exception has a great impact on reliability of flexible workflow system. This paper presented a stochastic Petri net based flexible workflow modeling and performance analysis method supporting exception handling，and took e-commerce systems in the logistics system for example, the flexible system's availability, reliability and other performance parameters were analyzed based on the stodrastic Petri net in modeling.

Key words: Exception, Flexible workflow, Stochastic Petri net, E-business