Nanofiltration is a kind of membrane separation technology between ultrafiltration and reverse osmosis. The pore size of nanofiltration membrane is between 0.5-2nm, and its separation mechanism is mainly pore size sieving and south effect, which can realize the selective separation of inorganic salts, amino acids and small molecular organic matter. Compared with ultrafiltration membrane, such as low molecular weight interception accuracy and high energy consumption of reverse osmosis, nanofiltration membrane effectively makes up for the shortcomings of both, but it is still in the stage of research and development, and it is difficult to customize the design and scale production.