In the process of radiation thermometer calibration, according to the verification regulation, the emissivity of radiation thermometers should be set to 1.00, while during the actual calibration process, the correction value of radiation thermometers with different emissivity values is required to give out by customers after the calibration and the emissivity is fixed and not equal to 1.00. In order to realize correction value calculation for wide-range radiation thermometers with arbitrary fixed emissivity in the calibration process, the article uses LabVIEW dichotomy iterative to achieve the integral algorithm of the plank formula and improves the degree of automation in the process of calibration effectively. The article verifies the difference of efficiency between dichotomy and common stepping algorithm, so that the correction value calculation could be efficiently implemented in any band, any emissivity, and any temperature point.