The qualitative and quantitative prediction for the dispersion of thermal discharge from nuclear / fossil power plant, steel works etc. has significant roles for the cooling system. Design and environmental management. In this study, the several important physical properties for the behavior of a thermal discharge with strong turbulent and buoyant effects are described. The comparative evaluation between MIT and PDS models is carried out, which have the different model structures. In general, MIT and PDS models are commonly used to calculate the thermal discharge behavior with considering the ambient current and the angle of jet in an unstratified water body. The simulated results by these models have great discrepancies due to the different assumptions in modling.