DFT/B3LYP calculations at 6-31G(d,p) basis set level and Tomas's PCM model and carried out for optimize the reactant and intermediate and production which is the reaction of Hydroquinone with Dimethyl Sulfate.Then(It's) single energy and charge density.According to calculatms result,to the best reaction condition is chosen,the rate of 4-methoxyphenol and 1,4-Dimethoxybenzene is limited to 1:0.16.