Urinary albumin is the main component of urinary protein, accounting for about 40-50% of the total. The amount of albumin excreted in urine is directly proportional to glomerular filtration, and excessive urinary albumin excretion mainly reflects the increased filtration caused by glomerular injury. Microalbuminuria is a higher than normal amount of albuminuria that cannot be detected by conventional methods. The detection of increased urinary microalbumin consists of the following three methods, whichever exceeds the normal range, is called increased urinary microalbumin: 1. urinary albumin excretion, the normal range is 20-200ug/min, which requires 4 hours of urine collection. 2. 24-hour urinary microalbumin, the normal range is 30-300 mg/24 hours, requiring 24 hours of urine collection. 3.Urine albumin/creatinine, normal range is 2.5-25mg/g, need to collect random urine. The most ideal method for measuring urine microalbumin is to retain a 24-hour specimen, but it is limited in practical application because of the difficulty of retention. Random urine measurement is currently the most commonly used and easiest method. In recent years, the detection of the albumin-to-creatinine ratio in the first urine of early morning or any urine instead of 24-hour urine protein quantification can avoid the effect of urine volume changes on the results. The increase of urine microalbumin in the usual urine examination is an early indicator of kidney damage, and its increase is of great value in the diagnosis of various kidney diseases and early kidney damage in hypertension and diabetes mellitus, and is a standard for clinical diagnosis and a target for treatment.