NOVELTY - N,N-Dimethyl aniline and dimethylbenzene solvent are provided into the reaction kettle, and provided into the ammonia gas. The crude ester is distilled into intermediate tank at flow rate of 200 kg/minute into the distillation column under high negative pressure of 0.098 MPa for distilling and separating, tower bottom temperature is controlled, and distilled and separated. The temperature of tower top is controlled, and the material is entered into the ammonium chloride triple effect evaporator for recycling ammonium chloride, to obtain trimethyl phosphite.    USE - Production of trimethyl phosphite (claimed).    ADVANTAGE - The trimethyl phosphite is economically and efficiently produced with high energy consumption, and low yield without polluting the environment.    DETAILED DESCRIPTION - 0.05% or less N,N-dimethyl aniline and dimethylbenzene solvent are provided into the reaction kettle, and provided into the ammonia gas. The temperature of the material is reacted in the reaction kettle at 15-20 degrees C to adjust the pH value of 6.5-7. The reaction is provided in the reaction kettle after removing the material content of alkaline solution to 6% in the weight ratio of 10:1, and water washing kettle is continuously injected. The pH value of water is controlled in the kettle to 9, and the temperature of water in the kettle is controlled at 15-20 degrees C. The washing material is dried at speed of 180 kg/minute into a continuous centrifugal separator, and ammonium chloride wastewater is separated out into the tower. The oil phase is separated and entered into a alkali tank at flow rate of 1 kg/minute into the second-stage centrifugal separator, separated wastewater is provided to water washing kettle with 30% alkaline water. The product of the solvent layer is separated and salt is dried into a dryer under pressure of 0.099 MPa. The film evaporator jacket is provided at 40 degrees C in hot water, and upper portion of evaporator and mixture of methanol are entered into the wastewater tank recycling methanol. The crude ester is distilled into intermediate tank at flow rate of 200 kg/minute into the distillation column under high negative pressure of 0.098 MPa for distilling and separating, tower bottom temperature is controlled at 80-90 degrees C, and distilled and separated. The tower top temperature is controlled at 60-65 degrees C. The wastewater is pre-heated by secondary steam at 80 degrees C at flow rate of 120 kg/minute, temperature is controlled at 100-105 degrees C, temperature of tower top is controlled at 90-95 degrees C, and the material is entered into the ammonium chloride triple effect evaporator for recycling ammonium chloride, to obtain trimethyl phosphite. The content of phosphorus trichloride is 99% or more. The content of methanol is 99.5%. The ratio of phosphorus trichloride, methanol, dimethylbenzene, N,N-dimethyl aniline and ammonia gas is 1:0.71:6.03:2.59:0.39. The input flow rate of phosphorus trichloride is 10 kg/minute. The flow rate of methanol is 7 kg/minute. The flow rate of solvent N,N-dimethyl aniline and mixed solution of dimethylbenzene solvent is 100 kg/minute. The flow rate of ammonia gas is 4 kg/minute. The lower film evaporator material is mixture of trimethyl phosphite and xylene, N,N-dimethyl aniline, and crude ester.