In order to provide the reliable step temperature signal in thermocouple time constant test, optimize the feedback control effect, further shorten the rising delay time of step temperature-rising signal and ensure the accuracy of thermocouple time constant measurement, the static temperature-voltage calibration was carried out for the high-speed radiation temperature measurement module by using medium-temperature blackbody furnace. The relationship between pulse width and temperature of single pulse width modulation (PWM) was obtained by heating the thermocouple with a laser. The nonlinear relationship between the voltage of infrared radiation thermometer module and the blackbody temperature, pulse width of PWM wave and temperature was analyzed theoretically. Experimental verification was provided for the further optimization of control effect and the establishment of system mathematical model. The results show that output voltage of infrared radiation thermometer module is quadratic to blackbody temperature and pulse width of single PWM wave is cubic to temperature. The experimental results can provide a theoretical basis for the controller to adjust PWM pulse width (duty cycle) by feedback control.