Polymers have desirable mechanical properties and have been widely used as structural materials instead of metals under severe mechanical conditions. The molecular chain network model based on J2-flow theory and Argon's hardening law cannot directly express a deformation-induced orientation of molecular chains, a propagation of high strain rate shear band and a nonlinear viscoelastic response before the initial yielding that is an inelastic behavior peculiar to polymer. In this paper, a new concept of “molecular chain slip system” is analogically proposed on the basis of crystal plasticity theory for metals. A molecular chain plasticity model that can reproduce the large deformation behaviors of glassy polymer mentioned above is developed by allowing an independent rotation of a slip system differently than the usual crystal plasticity framework. Moreover, the inelastic response law based on a probabilistic theory considering change of local free volume is adopted as a hardening law so as to express the nonlinear viscoelastic response.