1. The principle of reverse osmosis and osmotic pressure penetration penetration is a common phenomenon in nature, such as a cucumber into the brine, cucumber will become smaller due to water loss. Process cucumber water molecules into the saline solution is the infiltration process. If only water molecules with a permeable film in order to cut off a pool into two parts, at both sides of the membrane were injected into the water, and brine to the same height. Over a period of time can be found to reduce the water level, while increasing the level of brine. We put water molecules through the membrane into the brine phenomenon called penetration phenomenon. Salt level rise is not endless, to a certain height will reach an equilibrium point. Then both ends of the pressure difference in the level represented by the separator is called osmotic pressure. Size is directly related to the osmotic pressure and concentration of salt. 2. The phenomenon of reverse osmosis and reverse osmosis water purification technology to reach more devices in the balance, if applied some pressure on the salt water side surface, this time, the water molecules will migrate from salt water side to side. Process liquid molecules under pressure to the concentrated solution from a dilute solution of the migration phenomenon is called osmosis phenomenon. If more than one end of the brine is added facilities and over the saline osmotic pressure is applied to the end, we can get water at the other end. This is the principle of reverse osmosis water purification. The key production of pure water reverse osmosis facility has two, one a selective membrane, which we call semi-permeable membrane, the second is a certain pressure. Briefly, reverse osmosis semipermeable membrane has many holes, the size and the size of the holes the water molecules rather, due to bacteria, viruses, most of the organic pollutants and hydrated ions is much greater than the water molecules, and therefore can not penetrate through the reverse osmosis through the semi-permeable membrane and reverse osmosis membrane with the aqueous phase separated. Many kinds of impurities in water, soluble salts are the most difficult to clear. Therefore, often to determine the effect of the reverse osmosis water purification according to the level of desalination rate. Mainly determined by the level of reverse osmosis desalination rate of selectivity in the reverse osmosis semipermeable membrane. Currently, the high selectivity of the reverse osmosis membrane elements desalination rate can be as high as 99.7%.