The formation of intermediate and by-products in the synthesis of 4,4'-methylenedimethyldiphenylcarbamate (MDC) by the reaction of 4,4'-methylenedianiline (MDA) and dimethyl carbonate (DMC) over Zn(CH3COO)(2) catalyst was studied in this paper. The work would be of importance to deeply understand the reaction mechanism and to further improve the yield of aimed product. The intermediate and by-products were isolated from the reaction mixture and identified. The effects of reaction variables upon the formation of the compounds were examined. The mechanism on formation of the intermediate and by-products was proposed based on the experimental results.