Grinding and polishing process for polymethylmethacryla te（PMMA）is investigated based on previous proposed position/force control method of robotic automation grinding and polishing system. Through the analysis of the material removal mechanism of single abrasive grain，a model based on the elastic mechanic theory and Preston theory is proposed for predicting the surface of workpiece material removal volumes. The effect of different parameters on material removal volumes is investigated by conducting experiments，such as the polishing pressure，polishing tool rotational speed，feed rate，cutting cycles and abrasive grid size. The optimal processing parameters of the grinding and polishing for PMMA are determined by conducting the single factor experiments. Applying the processing of determined parameters，the surface deformation and microcrack of PMMA do not exist. The optimal surface finishing parameters can also meet the requirement of practical process.