Abstract: In this paper, the optimal control measures for average polymerization degrees of polyvinyl alcohol (PVA) were proposed by thoroughly analyzing the main influence factors. Based on the reaction mechanism of free radical polymerization and the large amount of production data, the quantification relationship of average polymerization degree of PVA with methanol ratio and conversion of polymerization was derived. With introduction of methanol ratio into the above equation, the quantification relationship among the polymerization exponent, methanol ratio, concentration of initiator and reaction time was further determined for a wider application scope. The optimal control was proved to have favorable effects on the polymerization average degree of PVA by practical production and development of multiple products.