When planing outfall system, the first target of design is to maximize initial dilution of discharge effluent. To achieve effectively this, it should be analyzed the characteristics of mixing phenomenon between ambient and discharged water. Especially the analysis at the Near-Field-Region(NFR) as initial dilution zone should be preceded. Usually, the initial behavior of effluent through outfall system is rising toward the surface due to mixing with ambient water for heat discharge and sinking toward the bottom due to the difference of density for brine discharge. After mixed with eddies accompanied by the ambient water, the plumes are showing the same density and internal current pattern by advection and diffusion. Until recently, lots of studies are being carried out for the optimum design of outfall system. but it is difficult to find anystudies of heat and brine discharge at the same time. Therefore, the initial behavior and NFR characteristics of heat and brine discharge at once have been examined in this study and it is hoped to provide some basic data for optimum design of outfall system.