In order to measure the temperature accurately using infrared thermal imager the interpolation of true surface temperature and the influence factors were studied. Based on the principles of thermal radiation and temperature measurement with infrared thermal imager

a general formula for computing the true surface temperature of objects was given. The influence of emissivity on accurate temperature measurement was discussed mainly

the conditions of accurate temperature measurement with infrared thermal imager were analyzed

and the influence factors from the surroundings

the atmosphere and the thermal imager were investigated too. Finally

the theoretical curves of the various factors influencing on the accuracy of measuring temperature were given.The results show that when emissivity is 0.7

the true temperature is 50℃

as deflected emissivity is 0.1

the measuring result of true temperature fluctuating is 0.76~0.89℃ for a 3~5 μm thermal imager; and 1.56~1.87℃ for a 8~14 μm thermal imager.It is shown that proposed method can provide a feasibility for improving the accuracy of measuring temperatrue and surface emissivity and reducing measuring errors.