Based on the principle of radiation temperature measurement, the theory of temperature measurement with infrared thermal imager is introduced, in order to improve the measurement accuracy of molten steel, an experimental platform is built, the infrared image of molten metal under different temperature are obtained. Through the wavelet denoising method for infrared image with high signal-to-noise ratio, display temperature and morphology is obtained by using Matlab software, which can reproduce the molten pool surface temperature field real, so as to achieve the requirements of measurement accuracy and design. This method lays a strong foundation for molten metal on-line infrared temperature measurement.