As one of the reverse osmosis membrane element series designed and developed by Originwater, the low-pressure series reverse osmosis membrane elements (RO-LP) are the core materials to realize reverse osmosis and mainly used for desalination of brackish water. The elements include low-pressure, ultra-low pressure, sea water desalination and antipollution series products and they are the core materials to realize reverse osmosis and mainly used to dispose of the industrial waste water with a little organic pollution, urban sewage and micro-polluted water source; the membrane element is composed of reverse osmosis membrane, central tube, inlet/outlet end cover, thick screen, light screen, fiberglass, seal, polyurethane sealant and other parts. The main material of DF nanofiltration filter element is polyamide composite membrane; it can make the hydrone and ionic mineral elements intercept the impure substances contained in water, such as pyrogen, bacteria, toxin , compound, heavy metals (arsenic, cobalt, cadmium, mercury, etc.) toxic substance, metal, salt, ions and other substances which do harm to body health and prepare the purified water through a layer of reverse osmosis membrane by using the booster pump for high-pressure penetration. Under the pressure of 0.45MPa and the recovery rate of 15%, the flux is ≧ 35L/m2 * h and the desalination rate for 250ppmNaCl solution is ≧ 90%; the reverse osmosis membrane can provide securer guarantee to the drinking water and it is particularly suitable for household and small water treatment devices.