Abstract: The tworeferencebody method can not measure accurately the emissivity of an object.According to the spectral response of an infrared thermal imager， a new precise measurement method with an infrared thermal imager was developed to measure the emissivity of an object. The determination of the parameter n in the tworeferencebody method is improved， and a new formula for emissivity calculation is obtained. Based on the analysis of the applicable conditions of the new measurement method， a measuring method to obtain accurate object emissivity is presented. Applications show that the measurement results are satisfactory.

Key words: infrared radiation, infrared thermal imager, temperature, emissivity, measurement technique