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. Urine low molecular protein accounts for about 70%, while albumin accounts for only 15-25%. Urine protein quantification is usually in the range of 1g/24h and rarely exceeds 2g/24h. Diagnosis can be aided by the following tests: 1. Urine protein clearance. 2, Selective protein index. 3, Urine sediment tubular examination. 4, Urine protein examination. 5, urine black acid qualitative test. Diagnosis is made by combining history, clinical manifestations and examination.