Detecting difference between process models is one of the key technologies in business process management. The classical graph edit distance cannot directly be used to detect the difference between process models because there are many kinds of nodes in a process model. To solve this problem

we present an algorithm for detecting difference between process models based on process structure tree. Firstly

the process models are converted to their corresponding task based process structure trees (TPSTs). Then the divide and conquer strategy is used to obtain the optimal mapped node set between two TPSTs. Finally

an edit script with approximate minimum cost is generated based on the mapped nodes

which is considered as the difference between two process models. The experimental results show that this algorithm can meet the real requirements in terms of precision and efficiency.