OpenMP regulates a series of compilation guidance, environment variables and runtime routines, having the advantages of simple operation, portability and supporting incremental parallel. But at the same time, the use of frequent thread management overhead FORK-JOIN model is one of the bottlenecks caused by OpenMP program performance constraints.. This article discusses how to use the merge and extend parallel zone, reconstruct the parallel section, and on this basis, using global process analysis ability which is provided by IPA, one of the Open64 optimization components, realize the parallel block mergeing which acrosses process boundaries. The final experimental results show that the method improves the performance of OpenMP programs effectively.