The paper put forward the teaching method combined PBL teaching method and case teaching method to resolve the problems that the satisfaction degree of postgraduates is lower, course contain is not closely related to practice. Taking the case course of underground engineering construction as an example, the concrete steps of PBL were detailed expounded including course content conformity, case design, PBL project design, planning, implementation, communication and evaluation. The difficulties of PBL were pointed out and the countermeasures were proposed. The practice shows PBL teaching method can increase the student abilities of autonomic learning, independent inquiry, engineering practice and innovation. It is propitious to train student's initiative spirits and group cooperative spirits.