This book presents the basic theories of Plastic Mechanics of Geomaterial, including the static and dynamic mechanical properties, nonlinear and classical plastic theory, yield surface theory, hardening model, flow rule and loading-unloading criterion, the calculation theory of principal stress axe rotation, and limit analysis of geomaterial and the latest advances in FEM limit analysis. It also set forth the typical static and dynamic constitutive model of geomaterial in detail. Broadening our understanding of the basic mechanical properties and constitutive model for geomaterial, the book helps readers to establish and select the most appropriate constitutive model according to the specific engineering problems and geomaterial characteristics. This book is a valuable resource for designers and researchers in fields related to geotechnical engineering, and it can also be used as a textbook for graduate courses.