An Integrated Hybrid Ocean Thermal Energy Conversion (I-H OTEC) system is one of the OTEC systems. This system is composed of electric generating plant and desalination plant. The submarine topography of east side of Kumejima region is suitable for arranging pipelines to take in deep ocean water. Therefore, Kumejima region is one of the place that is expected to construct an OTEC plant, and already OTEC experimental plant is under running. Okinotorishima region is also considered suitable for OTEC plant, because of its steep bottom topography and high sea surface temperature. In the present study, the analyses are conducted on the performance of Hybrid OTEC system adopting ammonia as a working fluid, that is using the results of oceanographic investigation carried out by the fisheries training ship. A procedure is developed to maximize a net power of power system consisting of heat exchanger under the condition of designate power system. The maximum net power is given by minimizing the heat exchangers which consume most of a power system. The minimum value of objective function decreases with the increase of the temperature difference between hot seawater and cold sea water.