NOVELTY - A glyphosate is produced by reacting depolymerized polyformaldehyde methanol solution with excessive glycine in the presence of triethylamine to obtain intermediate (I) methanol solution; subjecting intermediate (I) methanol solution and dimethyl phosphate to esterification reaction to obtain intermediate (II) methanol solution; desolventizing the intermediate (II) methanol solution; acidifying desolventized intermediate (II); and purifying, crystallizing, filtering and drying glyphosate reactant system.    USE - Method for producing glyphosate (claimed).    ADVANTAGE - The method applies purification of mother liquor to the purification process and crystallization process of glyphosate reactant system, in which the mother liquor is recycled without discharging to realize environmentally-friendly and clean production. Less formaldehyde is released to treat the side product of chloromethane and to make the process environment-friendly. The reaction temperature is low, and the reaction can be completely carried out at 80 degrees C which ensures conversion rate and prevents generation of side reaction, and improves yield and ensures high purity of the product.    DETAILED DESCRIPTION - Producing glyphosate comprises reacting depolymerized polyformaldehyde methanol solution with excessive glycine in the presence of triethylamine to obtain intermediate (I) methanol solution; subjecting intermediate (I) methanol solution and dimethyl phosphate to esterification reaction to obtain intermediate (II) methanol solution; desolventizing the intermediate (II) methanol solution, and recycling the recovered methanol and triethylamine after dewatering; acidifying the desolventized intermediate (II) in hydrochloric acid environment to obtain glyphosate reactant system, and to obtain side product of chloromethane; and purifying, crystallizing, filtering and drying the glyphosate reactant system to obtain high purity glyphosate powder. Purification of mother liquor is applied to the purification process and crystallization process of glyphosate reactant system.