Soil mechanics course has the characteristics of basic, epochal character and practicalness as a required course for geotechnical engineering. At present, the increasing demand and number of graduate students put forward higher requirements for theory and professionalism of soil mechanics. Therefore, it is necessary to carry out teaching exploration to expand the depth and breadth on the basis of the existing course content. Based on the teaching experience in soil mechanics, "shear strength of soil" in soil mechanics and "constitutive relation of soil" in advanced soil mechanics were connected. Focusing on introducing the critical state of soil, key points related to triaxial tests and soil properties were necessarily supplemented. The critical state analysis of sand soil was provided as an example, and the research on "microbial reinforced calcareous sand" was given as an aid. This paper introduced how to expand the study points of soil mechanics and how to introduce the subject frontiers. This helps the students understand and consolidate the basic theoretical knowledge, stimulate and cultivate students’ interest and ability in independent learning, and create good basic conditions for further study.