Abstract: Where as some scholars commented on the generalized plastic mechanics(GPM) and put forward their doubts and opinions,some further interpretations of GPM were presented and its origin and essential ideas were expatiated clearly.The isotropic hardening model,which was commonly adopted in classical plastic mechanics and GPM,and the physical meaning of yield surface were analyzed deeply.Some problems,such as rate-independent plasticity,Drucker postulate,sign of plastic coefficient,convexity and uniqueness of yield surface and so on,were answered and discussed.