Water is a very important resource for all living things on earth. Humans are often faced with a problem that is the difficulty of finding a source of fresh water during the dry season. Especially people who live on the coast and small island islands. The purpose of this research is to make appropriate technology that benefits the coastal communities by using a filtration method that uses materials derived from nature, and ionization which utilizes ion exchange using cation resin. Another purpose of this process is to reduce salt levels which can cause corrosion of the pumping machine and prevent damage to the membrane membrane. The seawater samples used were taken from the same beach in Bantul Regency. Zeolith and cation resins are activated before being used in this process, so that the ionization and filtration process can work optimally. Sea water. Zeolith activation and cation resin use a mixture of chemicals namely Chloride Acid (HCl) and Sulfuric Acid (H2SO4) solutions. From samples taken in July-October 2018 tds of seawater were 19,000 ppm. In the process of filtration and ionization can reduce TDS (Total Dissolve Solid) by 39.6%. It takes 3600 seconds or 1 hour to produce processed water with a capacity of 180 L then channeled to the pumping machine to pass through the reverse osmosis membrane