To study the best extraction method and process of volatile oils of peppermint leaves from Xiaoyao granules.Methods：The optimum process was determined by a single factor method combined with an orthogonal test with the amount of volatile as determination marker.Results：The results indicated the optimal water-extraction process was as follows：the water amount was 12 times of the traditional Chinese drugs; the soaking time was 4 hours; the extraction shall last 4 hours.Conclusion：Considering the demand of manufacture，the extraction process is rational，practical and effective.