Proteinuria is a typical symptom of chronic kidney disease, and the cause of proteinuria is inextricably linked to the glomerular barrier function. Glomerular capillaries are composed of three layers, from inner to outer, namely endothelial cell layer, basement membrane layer and epithelial cell layer. Since these three layers of cells are distributed with varying sizes of pores and negative charges, the barrier function of glomerular capillaries can be divided into two types, i.e., mechanical barrier – pores and charge barrier – negative charges. Low molecular proteinuria is due to the impairment of renal tubular function, so that the normal glomerular filtration of protein back absorption obstacles. Low molecular protein accounts for about 70% of the urine, while albumin accounts for only 15-25%. Urine protein quantification is usually 1g/24h, rarely more than 2g/24h. Medical history History of edema, hypertension, diabetes mellitus, allergic purpura, renal damage, heavy metal salts, connective tissue disease, metabolic disease, and gouty episodes. Physical examination: attention should be paid to edema and plasma membrane fluid, bone and joint examination, anemia, and cardiac, hepatic, and renal signs. Fundus examination, acute nephritis fundus is normal or mild vasospasm, chronic nephritis fundus arteriosclerosis, hemorrhage, exudation, etc. Diabetic nephropathy often appears diabetic fundus.