For IV、V、VI levels of weak rock， because of different levels， The calculated load of tunnel surrounding rock according to the relevant specification was too different. Based on surrounding rock sub-classification method of current highway tunnel， the relation between the new surrounding rock classification and the elastic p-wave velocity refining that was used by railway tunnel was built. The phenomenon of elastic p-wave velocity cross overlap was avoided when surrounding rock classification was different in railway tunnel. For Ⅲ、V、V、VI levels of weak rock， the further refining was done by Vp in railway tunnel， in order to calculate primary support design pressure of surrounding rock， so the oversize difference of computation load value Between adjacent classification was avoided. Combining with a subway tunneling of Qingdao， comprehensive fuzzy identifying method is used to judge Surrounding rock classification level of refinement and adjust， which is more safe and economical for design and construction.