N70 nanofiltration membrane has nanoscale pore size, which can allow water to completely pass through while intercepting or partially intercepting substances with higher molecular weight than water. Its removal rate for NaCl is 50-85%, and the removal rate for MgSO4 can reach 98%. It can be used for softening, purification, wastewater purification treatment, and concentration and separation of valuable components in process material solutions for drinking water and industrial water. Its retention rate for electrically neutral polyethylene glycol with a molecular weight of 200 daltons reaches 90%, making it also suitable for the separation and concentration of organic components such as COD and BOD. It can effectively remove organic substances such as insecticides, herbicides, THM precursors, as well as bacteria and viruses from water.