In clinical practice, it is often encountered that when a positive urine protein is found in a routine urine test during a health check-up, one is overwhelmed and seeks medical help everywhere, causing a lot of psychological stress. In general, the presence of positive protein in urine tests is often a sign of some kind of disease, which can be accompanied by abnormalities in blood biochemistry and ultrasound and other aspects of the test, and requires prompt medical attention to identify the cause for symptomatic treatment. However, not all proteinuria is caused by disease. This kind of proteinuria is often referred to as functional proteinuria, and there are several types of proteinuria in clinical practice. Mostly seen in young people, under the influence of strenuous exercise, high temperature, cold, mental stress and other factors, the renal vascular spasm or congestion, resulting in increased permeability of the glomerular filtration membrane and a large amount of protein “leakage”. The protein in the urine of pregnant women may increase mildly, which is related to the increase in body position and renal flow and glomerular filtration rate, usually not more than 24 hours. After the trigger is removed, the proteinuria will disappear on its own. Postural or upright proteinuria refers to an increase in urinary protein excretion only in the upright position or when the spine is in an anterior protrusion position, while the urinary protein excretion is normal in the recumbent position. It can be divided into temporary (or intermittent) and fixed according to whether the upright urine protein appears frequently, the former refers to the upright position when the urine protein does not necessarily increase every time, the latter refers to the upright position where the urine protein excretion is more than normal. Upright proteinuria is more common, mostly in adolescents, and less common after the age of 30. Most of the asymptomatic proteinuria found in population screening falls into this category. Among them, 70% to 80% are transient and 15% to 20% are fixed. Persistent benign proteinuria refers to the normal range of blood sedimentation, blood chemistry, renal ultrasound and renal histological examination, and generally no other symptoms. This type of proteinuria can account for 5% to 10% of patients with asymptomatic proteinuria in the census. Clinical diagnosis of persistent proteinuria as “benign” should be very cautious, because some glomerular diseases or their early stages may only show persistent proteinuria (such as thylakoid nephritis, membranous nephropathy, nephrosclerosis, diabetic nephropathy, etc.), which often requires intensive follow-up and further examination. Therefore, if proteinuria is found, a professional doctor should be consulted to make a diagnosis after a comprehensive analysis with medical history and physical signs.