Abstract: Based on the Talreja's damage model with tensor valued internal state variables, the constitutive relations for the plane stress problems of composite uni-ply plates with damage are derived. The nonlinear postbuckling equilibrium equations of those plates with initial deflection are obtained. The unknown functions are separated by using the finite difference method in the space domain, and the time is equally divided into small time intervals. All the nonlinear items are linearized, and the separated equations are solved iteratively. Numerical results show that damages continuously reduce structural rigidities, which causes postbuckling deflections of plates increase as time goes on.