In recent years, PBL is one of the education models that attracts much attention in the field of education. With the deepening of education reform, the PBL teaching model has been applied and researched in the field of civil engineering teaching to a certain extent. Tunnel and underground engineering, as an important component of the civil engineering major, is characterized by a wide range of knowledge, strong practicality and great difficulty. In order to promote the teaching quality and the deep integration of new teaching modes with practical education and teaching, the research applies the PBL teaching model to the teaching of underground structure design principle and method in the tunnel and underground engineering major. Combining with actual teaching experience, reforms are carried out from teaching content and teaching implementation principles, and four basic principles of applying the PBL teaching model in tunnel and underground engineering education practice are put forward: theory combined with practice principle, step by step principle, enlightening principle, and intuitionistic principle. Through educational practice, it is found that under this teaching mode, students’ interest in learning, sense of learning acquisition and achievement have been greatly improved, they have a more profound grasp of the corresponding knowledge system, and the actual teaching effect has been greatly improved.