The synthesis of dimethyl carbonate (DMC) from methanol and supercritical carbon dioxide over K2CO3/ZrO2 catalysts have been studied. The catalysts were prepared by impregnating ZrO2 with an aqueous K2CO3 solution. The optimum calcination temperature to disperse K species on the ZrO2 surface was found to be 673 K. Monoclinic ZrO2 was not active, as itself, for the DMC production. However, when the K2CO3 was impregnated on the ZrO2, the catalytic performance was improved. Besides the catalyst, CH3I was used as a promoter. The CH3I promoter as well as the K2CO3/ZrO2 catalyst was found to take an important role to improve the production of DMC. The optimum quantities for the catalyst and the promoter were estimated. The effect of the catalyst and the promoter for the DMC synthesis from methanol and supercritical carbon dioxide was investigated and the reaction mechanism was proposed.