An algorithm of temperature model based on infrared image is proposed.Firstly,the infrared image in special time is collected by infrared thermograph,and the temperature is obtained.Secondly,the temperature of the vehicle′s special part in any time is gathered through two calculation processes which are temperature to radiation conversion and radiation to temperature conversion.Experimental results show that the results are consistent with the practical measured results and have high operational precision.The method also can be applied to other fields.