Abstract：The generalized plastic mechanics developed from the traditional plastic mechanics can reflect the real deformation mechanism of geomaterials. According to the generalized plastic mechanics，the constitutive model is composed of three plastic potential surfaces and three corresponding yield surfaces. The relationship between the yield surface and the plastic potential surface is discussed systematically，and the basic characters of yield surface，especially of volume yield surface that can calculate dilatant volume strain and shear yield surface in stress Lode angle direction，are also discussed.
