Asymmetric reverse osmosis(RO) composite membrane, which are organic/inorganic RO composite membranes by new mode, based on cellulose acetate and polyamide with nano particle tourmaline substance in order to develop a new desalination membrane having high selectivity and permeability were prepared. The practical separation performances of new RO composite membranes were investigated on seawater desalinization, especially for deep ocean water. The separation characteristics of new RO composite membranes were discussed with the variation of applied pressure and temperature. The permeation flux of new RO composite membranes was investigated using module unit composed of RO plate-frame type modules and spiral wound type modules. The rejection and the flux for new RO composite membrane were $99.0{sim}99.3%;and;7.0{sim}23.3l/m^2$ hr in deep ocean water at $20^{circ}C$, respectively. In addition, the separation performance of new RO composite membranes for deep ocean water was very steady-state with long experiment time.