NOVELTY - Producing potassium salt of glyphosate solution from glyphosate mother liquor comprises adding sodium hydroxide solution or potassium hydroxide solution to glyphosate mother liquor, adjusting to pH 9.0-11.0, separating triethylamine to obtain sodium or potassium mother liquor; filtering and separating mother liquor by multi-grade nanofilter film and carrying out film processing to obtain concentrated liquid; adding raw or wet glyphosate, potassium hydroxide and glyphosate additive to the film-processed concentrated liquid to obtain solution containing higher than 30% glyphosate.    USE - Method of producing potassium salt of glyphosate solution from glyphosate mother liquor (claimed) for use as fertilizer.    ADVANTAGE - The method supplies potassium fertilizer and phosphate fertilizer to crops during weeding without influencing the environment. It maintains the normal production of glyphosate containing potassium and phosphorous acid salt.    DETAILED DESCRIPTION - Producing potassium salt of glyphosate solution from glyphosate mother liquor comprises    (A) adding 25-40% sodium hydroxide or potassium hydroxide solution to the mother liquor to neutralize, adjusting to pH 9.0-11.0, separating triethylamine on upper layer, recovering triethylamine on lower layer by rectifying to obtain sodium or potassium mother liquor;    (B) filtering and separating sodium or potassium mother liquor by multi-grade liquid nanofilter film, concentrating and separating the mother liquor, carrying out film processing to obtain concentrated liquid containing 1.0-10.0% glyphosate and smaller than 5% sodium or potassium chloride and dilute liquid containing 0-1% glyphosate and higher than 5% sodium or potassium chloride; and    (C) adding raw or wet glyphosate, potassium hydroxide and glyphosate additive to the film-processed concentrated liquid and preparing into the potassium glyphosate solution containing higher than 30% glyphosate, where the weight ratio of the film-processed concentrated liquid to the raw or wet glyphosate to potassium hydroxide to glyphosate additive is 12-50:30-50:10-35:6-12 and the additive is alkyl glucoside, amine ether and/or polyethylene glycol.