The spreading of hot waste water discharged from the coastal power station is a new problem to marin e circumstances and the fishery. Because the survey of hot waste water discharges should be performed is multaneously across wide areas, it is very difficult. Some sensors of the Landsat can draw the spread and distribution of water temperature from wavelength range of thermal infrared. The present study applied the GIS after stretching DN for the purpose of drawing a more accurate distribution of water temperature. Accordingly, the pattern of water temperature distribution could be expressed more precisely for a broad area, and the spread and distribution of hot waste water could be analyzed economically.