The appearance of measurement error is inevitably caused by steel rolling, steel slag, steel scale in the temperature monitoring of molten steel in RH refining furnace. Through the accurate discrimination and cluster analysis of the molten steel and non steel material, such as design, key parameters of the sampling area, gray value correction and the temperature model, the actual temperature of the molten steel can be obtained, and temperature variation curves are given to improve the accuracy and continuity of temperature measurement, and easily achieve precision steelmaking and scientific steelmaking.