Abstract: The primary rate of the polymerization of methyl methacrylate (MMA) initiated by the mixture of N, N-dimethylaniline (DMA) and benzyl chloride (BzC1) was found to be affected notably by the polarity of the solvents used. In aprotic solvents, the sutstituent present on the benzene ring of DMA, no matter what origing it is, either an electrondonor or an accepter, will low the rate of polymerization more or less; however, in the case of protonic solvents, the rate will be enhanced by the substituents of an electron-donor, and vice versa. When the polymerization is initiated by a quaternary ammonium salt (I) composed of DMA and BzCl, its primary rate will vary with the square root of the concentration of I. The apparent overall activation energy of the reaction is 71.5 kJ/mol. Confirmed by the UV-analysis, the residual part of DMA was found joined to macromolecules proper of the polymers formed when the polymerization was initiated with DMA-BzCl or quaternary ammonium salt as mentioned.