The invention belongs to the technical field of chemical synthesis, and particularly relates to an optimized preparation method of N-methylmorpholine-N-oxide. The N-methylmorpholine-N-oxide (NMMO) isan organic solvent in a cellulose spinning process. The synthesis methods commonly used in the field mainly comprise a hydrogen peroxide peroxidation method and a molecular oxygen-aldehyde catalytic oxidation method; wherein the hydrogen peroxide method is widely applied due to the advantages of mild reaction conditions, high product quality and the like, and catalysts commonly used in the conventional hydrogen peroxide catalysis method comprise basic ion exchange resin, copper hydroxide, manganese dioxide, quaternary ammonium salt compounds and the like; however, these catalysts have higher requirements on the reaction conditions. Researches show that when titanium dioxide is used as a catalyst, the temperature for preparing N-methylmorpholine-N-oxide can be reduced, the yield of N-methylmorpholine-N-oxide is greatly increased, the reaction temperature is only 40 DEG C, and the yield can be increased to 90%; so that the production energy consumption is reduced, and the method has goodindustrial production and popularization significance.