Urine acidity is not only the PH value of urine, but also reflects the ability of kidney to adjust the acid-base balance of body fluids. Under normal dietary conditions, the urine pH value is 4.6-8.0 (average 6.0), which is mainly determined by the factors such as the secretion of H+ by renal tubules, the secretion of titratable acid, the formation of ammonium and the reabsorption of bicarbonate. The most important thing is the expansion of acidic phosphate or its relative content to alkaline phosphate. If the former is more than the latter, the urine will be acidic and neutral.