Protein in urine of patients with nephrotic syndrome mainly comes from their blood. Under normal circumstances, most of protein in the blood of patients with renal pain syndrome will not appear in urine, especially protein and negatively charged protein, because there is a filtration barrier in glomerulus, which hinders the filtration of protein. When cold, fatigue and other inducements act on people with weak disease resistance (that is, clinically speaking, the body's immunity is low), it is easy to cause inflammatory reactions in different kidney tissues such as glomerular capillary endothelial cells, visceral epithelial cells, basement membrane, etc., and destroy the barrier structure that normally hinders the protein filtration of the kidney, resulting in pathological changes in the filtration function of the glomerulus, and the filtration aperture of its glomerular filtration barrier becomes larger, and a large amount of protein is filtered into urine from the glomerular basement membrane. In nephrotic syndrome, due to various pathological factors, the barrier function of filter membrane is destroyed, such as the increase of pore size or the decrease of negative charge, which leads to a large amount of protein leakage, far exceeding the reabsorption capacity of renal camp, so a large amount of proteinuria occurs.