Abstract: According to spectrophotometer method from GB/T 6437-2002,feed total phosphorus was determined by using combining with a concentration feed and a mixed feed.The result showed that the tested specimen dissolution fluid was turbid,it should be precipitated over night by steting and attract clarified liquid to carry out the examination,the examination result is more accurate and reliable.If the tested specimen dissolution fluid was clear,the detection results between day and precipitated over night were the same.This experimental technique will useful for consummating the method for feed total phosphorus detection.