Effects of process parameters on polymethylmethacrylate (PMMA) elastic recovery by hot compression experiments were researched. The results show that temperature and time are important factors to affect PMMA elastic recovery obtained from the experiments. Maxwell equation was generalized as the control equation of stress relaxation, and the fitting stress relaxation curves show high coincidence degree with the curves tested by experiments. The model of elastic recovery rate was derived from Maxwell equation, and the prediction error of the model to PMMA elastic recovery is less than 10%.