In order to deal with the complexity of large sy stems

the divide and conquer policy is adopted in requirements engineering:collect requirements from different groups of stakeholders

and then compose them together as a complete requirements specification.However

the policy brings forward the problem of overlapping use cases:similar event flows appear in more than one use case.Duplicate event flows lower the readability and maintainability of use case diagrams.The problem has been recognized

but no detecting approach is available to find out duplicate event flows.The paper propo ses a heuristic algorithm which is based on information retrieval technologies.Evaluation results suggest that the algorithm is efficient and effective.