Diabetes mellitus (DM) has become one of the major diseases that endanger human health. Diabetic nephropathy (DN) is one of the most main microvascular complications of diabetes and is a common cause of end-stage renal disease. Change in microalbuminuria level has long been considered a hallmark of DN development, but some diabetic patients have renal pathological changes, while microalbuminuria is in the normal range. This suggests that microalbuminuria is not an ideal indicator for early detection of DN. Studies at home and abroad have shown that serum neutrophil gelatinase-associated apolipoprotein (sNGAL) is closely related to the development of DN, sNGAL can be detected before the appearance of microalbuminuria and is more sensitive and specific than microalbuminuria. Therefore, sNGAL is expected to become a new biomarker for the diagnosis of early DN.