The invention discloses a method used for separating and extracting lactic acid from a fermentation broth. The method comprises following steps: (1) the fermentation broth is subjected to filtering, acidolysis, and heating concentration dehydration so as to obtain a preliminarily concentrated lactic acid solution; (2) active carbon is used for decolouring of the preliminarily concentrated lactic acid solution, a small amount of an alcohol with a high boiling point is added, and concentration dehydration is carried out until lactic acid content is higher than 90%; (3) the lactic acid concentrated solution is cooled to 10 to 15 DEG C, an acetate is added, an alcohol precipitation agent is added with stirring until temperature is reduced to 4 to 10 DEG C, and a lactic acid filtrate and a solid substance are obtained via filtering; (4) the solid substance is washed with ethyl alcohol, and a precipitate and a lactic acid filtered solution are obtained via filtering; (5) the lactic acid filtrate obtained in step (3) and the lactic acid filtered solution obtained in step (4) are subjected to distillation; and (6) a lactic acid liquor obtained in step (5) is subjected to molecular distillation refining so as to obtain a lactic acid product. In the method, conventional desalting and deproteinization processes such as ion exchange and ultrafiltration are avoided, so that lactic acid loss in the fermentation broth is reduced, and lactic acid yield and quality are improved.