A computational procedure for analyzing the deformation and fracture of solid polymers is developed based on a molecular chain model. In the model, the polymer solid is represented by a network of nonlinear elastic chains. Cellular automata modeling is employed to generate the network of polymer chains. Van der Waals and viscous forces acting on the chains are taken into account and are approximated to act at the nodal points of the network. A stiffness equation is derived by employing the principle of virtual work, in which geometrical nonlinearity due to a large deformation is considered. Slippage and scission of chains are also taken into consideration. The effects of molecular weight distribution and molecular chain scission due to UV-degradation are discussed.