NOVELTY - Preparation of glyphosate comprises alkylating dimethyl phosphate to obtain glyphosate and glyphosate mother liquor; treating mother liquor; preoxidizing, degrading and extracting to obtain concentrated solution and salt liquid diluted solution; decolorizing concentrated solution, concentrating and polymerizing; nanofiltering salt liquid diluted solution to obtain concentrated and diluted solution; returning concentrated solution to preoxidation; introducing diluted solution in mechanical vapor recompression system, obtaining sodium chloride, water and mother solution; and reusing products.    USE - Method for preparing glyphosate (claimed).    ADVANTAGE - The method has low production cost, enhances utilization ratio of products, reduces waste in glyphosate process, environment-friendly and has economic and social benefits.    DETAILED DESCRIPTION - Preparation of glyphosate comprises    (A) reacting dimethyl phosphate by in alkyl ester reaction to obtain glyphosate and glyphosate mother liquor;    (B) neutralizing glyphosate mother liquor with liquid alkali and triethylamine to obtain alkali mother liquid and distilling to obtain second mother liquor;    (C) adjusting pH of second alkali mother liquid with caustic soda, carrying out catalytic oxidation, high temperature and high pressure air electrocatalytic degradation and liquid membrane extraction to obtain liquid membrane concentrated solution and salt membrane diluted solution;    (D) adding sodium carbonate to concentrated liquid, subjecting to activated carbon to discolor, evaporating, concentrating and crystallizing to obtain sodium phosphate tribasic dodecahydrate, carrying out high temperature polymerization to obtain sodium triphosphate; filtering salt membrane diluted solution in one to three nanofiltration membrane to obtain membrane concentrated solution and membrane diluted solution;    (E) returning of membrane concentrated solution to the catalytic preoxidation step (C) for recycling; entering of membrane diluted solution to mechanical vapor recompression (MVR) system for concentration by evaporation and obtaining sodium chloride crystal, distilled water and mother solution;    (F) adding deionized water to sodium chloride crystal to obtain pure sodium chloride crystal and cleaning liquid, recycling cleaning liquid in MVR, adding sodium hypochlorite to pure sodium chloride crystals to oxidize to obtain brine, carrying out electrolysis using brine to obtain sodium hydroxide solution, chlorine and hydrogen; using sodium hydroxide solution and solid sodium hydroxide in step (B) for triethylamine recovery process or sodium hydroxide solution used to neutralize in alkyl ester process and processing dilute methanol and recycling chlorine, hydrogen and hydrochloric acid in glyphosate production;    (G) introducing of distilled water obtained in step (E) in stripping deaminization tower to obtain 2-8% ammonia water and ammonia water of less than 50-200 mg/L in nitrogen depleted water, using ammonia water for processing glyphosate ammonium salt and using nitrogen depleted water for processing glyphosate process water; and    (H) mother liquid obtained in step (E) is 1-20 wt.% of mother liquor obtained in step (C) for catalytic oxidation reuse.