Protein levels in the urine above the normal range are called proteinuria, which is generally considered to be diagnosed in children with a 24-hour urine protein quantification greater than 150 to 200 mg. Pediatric proteinuria can be divided into four major categories: functional proteinuria, postural (upright) proteinuria, persistent asymptomatic proteinuria, and pathologic proteinuria. Functional proteinuria is a mild, transient, benign proteinuria. There is no organic damage to the renal parenchyma. If transient proteinuria occurs during fever, urinary protein disappears after the fever subsides. Protein in the urine may increase transiently after exercise, especially in adolescents after long-distance races, swimming, soccer, basketball, etc., and may disappear after adequate rest. Postural (upright) proteinuria is a negative urine protein test before waking up in the morning, which gradually appears after getting up and moving around, and disappears again after lying down and resting. The urine protein level usually does not exceed 1 gram in 24 hours and has a good prognosis, and is rare after the age of 30. The mechanism of its occurrence may be the compression of the inferior vena cava by the posterior border of the liver and spine during standing, resulting in temporary renal stasis and obstruction of lymphatic return. Persistent asymptomatic proteinuria occurs independent of body position, usually without other systemic symptoms such as swelling, and all relevant laboratory tests are normal, and pathological examination by renal puncture is not abnormal. Pediatricians are very cautious in diagnosing persistent asymptomatic proteinuria, as some glomerular diseases or their early stages may manifest only as persistent proteinuria. It is important to visit the hospital regularly for appropriate investigations. Pathological proteinuria is caused by various glomerular or tubular diseases. Such as acute, prolonged, chronic glomerulonephritis, purpura nephritis, interstitial nephritis, nephrotic syndrome, drug-related kidney damage, etc. Therefore, routine urine examination of children, occasional protein, parents do not have to be overly nervous, to first rule out functional proteinuria, can be re-examined after a week, if the urine protein turns negative, then you can rest assured; if there is still proteinuria, but also to rule out postural proteinuria, should go to the hospital for the appropriate examination. For persistent asymptomatic proteinuria, there is no need to rush treatment. Under the guidance of a specialist, regular check-ups, avoid straining and prevent respiratory infections are needed. For proteinuria lasting more than six months, it is best to have a kidney puncture to understand whether there are pathological changes in the glomerulus and decide whether to carry out the corresponding treatment. Proteinuria accompanied by hematuria, scanty urine, swollen eyelids and limbs, hypertension, mostly glomerulonephritis; significantly higher proteinuria, swelling, elevated blood cholesterol and lower plasma protein, mostly nephrotic syndrome, should immediately go to the hospital for active treatment.