The present invention discloses a method for measuring the surface temperature of a high-temperature casting blank in water-fog medium; the water-fog concentration of the surface of the high-temperature casting blank is measured and transmitted to a remote computer through an air water-fog concentration sensor; the attenuation coefficient K lambda of water-fog medium to radiant energy in the water-fog concentration is gained by the remote computer through the relation curve between the attenuation coefficients of the water-fog medium and the radiant energy; temperature data tested by a thermodetector are modified by the attenuation coefficient K lambda and the emissivity of filam on the surface of the casting blank and the real temperature of the surface of the casting blank in the water-fog medium can be measured in real-time; the gain of accurate temperature has an important support on the application of continuous casting front-edge technology such as electromagnetic mixing, secondary cooling dynamic control and so on in dynamic slight press and has very important significance on improving the quality of casting blank and the whole level of continuous casting.