The declines of river corridor vegetation density strongly affect to the river heat environment, and that change makes big impact to the ecological systems. In this study, stream temperature analysis model related with river corridor density was developed and applied to Nam Song River, Laos. Metrological data (air temperature, relative humidity, wind speed) were used, and sink or source terms of heat transfer equation were estimated from those data. Land cover GIS data was used for vegetation density analysis along the main river. As the result of simulation cases with several vegetation densities, river water temperature was more sensitive to river discharge change as decreasing of vegetation densities.