NOVELTY - Separating and recovering oxalic acid from oxalic acid waste liquid comprises e.g. filtering borneol production waste oil acid washed produced waste water to obtain oxalic acid-sodium oxalate mixed crystal residue, transforming mixed crystal residue into oxalic acid, adding hydrochloric acid solution, dissolving oxalic acid-sodium oxalate mixed crystal, separating solid sodium chloride, absorbing upper layer, filtering, obtaining oxalic acid-containing solution and sodium chloride crystals, and sodium chloride as the product, allowing oxalic acid containing solution to stand to crystallize.    USE - The method is useful for separating and recovering oxalic acid from oxalic acid waste liquid (claimed).    ADVANTAGE - The method can recover valuable components in waste water; does not generate waste water and waste residue throughout the process; realizes anhydrous oxalic acid purity of more than 99.8% and oxalic acid total recovery rate in waste water of more than 99%; has high efficiency; is economical; assures good working environment; and is suitable for industrial application.    DETAILED DESCRIPTION - Separating and recovering oxalic acid from oxalic acid waste liquid comprises (i) separating and recovering oxalic acid-sodium oxalate mixed crystals and sodium sulfate crystals: filtering borneol production waste oil acid washed produced waste water to obtain oxalic acid-sodium oxalate mixed crystal residue, (ii) transforming step (i) obtained oxalic acid-sodium oxalate mixed crystal residue into oxalic acid of theoretical amount, adding 1-6 times of hydrochloric acid solution, dissolving oxalic acid-sodium oxalate mixed crystal, separating out solid sodium chloride, absorbing the floating upper layer of overlapped oil, filtering, obtaining oxalic acid-containing solution and sodium chloride crystals, and sodium chloride as the product, and (iii) refining oxalic acid: allowing oxalic acid containing solution to stand at 0-20 degrees C, so that oxalic acid crystallizes, filtering to obtain oxalic acid crystal and oxalic acid crystallized mother liquid.