Abstract: For the polymer production industries, the competitive edge will come from the technology that excels in controlling the polymer quality in a consistent way over the entire plant. The state of the art quality control systems of polymer production plant is reviewed，with the main focus on on–line soft–sensing and optimal grade transition control problems. It is proposed that the most important factor in developing an intelligent quality control system is quality modeling and implementing plant–wide quality estimation and control is beneficial. Finally, some open problems and potential development trends of the field are pointed out．