Phosphoric acid is an important chemical raw material.At present,the method of producing phosphoric acid and phosphate mainly adopts wet-process,but wet-process phosphoric acid contains a large amount of impurities.In the process of purifying wet-process phosphoric acid by solvent extraction,a large amount of metal ion impurities precipitate in the form of insoluble phosphate precipitate,and the problem of recycling of insoluble P₂O₅ has received widespread attention.Alkaline hydrolysis process was used and single factor experiment was designed,the effect of liquid-solid ratio,n（Na₂O）/n（P₂O₅）,reac-tion temperature and reaction time on the wet-process phosphoric acid extraction residue（insoluble metal phosphate） deco-mposition were inspected,and a suitable range of reaction condition was selected.On this basis,the optimal reaction conditions were obtained through quadratic regression orthogonal experiments.The results showed that the optimum conditions were con-firmed as following：liquid-solid ratio was 30 mL/g, n（Na₂O）/n（P₂O₅）was 3.31,reaction temperature was 82 ℃ and reactiontime was 4.05 h.Under optimum conditions,the recovery rate of P₂O₅ could reach 92.48%.The reaction lye could be further used as raw material for the production of trisodium phosphate.In this study,a reasonable scheme for purifying phosphoric acid extraction residue was obtained,and related parameters were given,which provided guidance for the practical applica-tion of this program.It was of great significance for the utilization of extraction residue and environmental protection.