Abstract: Many types of Karsts can be encountered when a tunnel in Karst ground was constructed.Generally the primary design classification of the surrounding rock mass should be revised according to the excavation condition.A classification methd for rock mass surrounding Karsts is put out in this paper.Several general conceptions about the rock classification are described.The classification standards are based on the correction coefficient of Karst development degree.The Wulong tunnel at Hengdong section is used as an example.The application shows that the classification with this method agrees well with the findings during the tunnel construction.In the method,the synthesis factors such as possibility of Karst development and Karst forms are considered.The method is the correction of the origin classification methodsthe rock surrounding Karsts.The method still needs to be verified in the future practice.examined.