The invention relates to a production method of triethyl phosphite, which belongs to the technical field of chemical production. Absolute ethyl alcohol, phosphorous trichloride are taken as main material, pure benzol is taken as solvent, triethylamine is taken as acid-binding agent, liquid ammonia is taken as reducing agent, and the triethyl phosphate is prepared through the processes of three-complex liquor preparing, synthetic reaction, water scrubbing reaction, layering, drying, crude distillation, rectifying, recovering and ammonia recovery and the like. The method adopts continuous production process of triethylamine, the material charging and the product discharging are continuous, the production capacity is strong, and the product quality is stable. With equal equipment and investment, the capacity of the method can be 6 to 7 times as the capacity of intermittent method. The method solves the problems of the prior production method that the production capacity is small, the production cycle of the product is long, the material consumption is large, the quality is unstable, the discharge amount of 'three wastes' is large, and the yield can not be guaranteed. The method has the advantages that the liquid ammonia is taken as reducing agent, the cost is low, the recovery factor of excess ammonia can reach more than 90 percent, the recovered ammonium chloride can be used as the crude product of ammonium fertilizer, the production cost is lowered, and the environmental pollution is reduced.