The quinoline phosphomolybdate gravimetric method is accurate and precise in measuring high-content phosphorus samples,but it is not suitable for the determination of low-priced phosphorus compounds.In order to solve this defect,a new method was proposed：the hypophosphite was oxidized first and then determined,the appropriate oxidant and oxidation and precipitation conditions were explored.Experiments showed that cerium ammonium nitrate could be used as an oxidant before the formation of quinoline phosphomolybdate,which could quantitatively convert low-valent phosphorus into high-valent pho-sphorus so that low-valent phosphorus could be measured in response to the precipitation agent,in order to ensure complete conversion of low-valent phosphorus.The excessively added cerium ammonium nitrate should be heated to boiling for more than 20 minutes to remove it,otherwise it would affect the subsequent operation.This method could detect the orthophosphoric acid content,total phosphorus content,and hypophosphorous acid content of complex samples containing multiple forms of phosphorus at the same time,and had good practical application value.