In order to provide more accurate step temperature rise signal in thermocouple time constant testing, optimize the control effect, and improve the accuracy of thermocouple time constant measurement, Tornambe controller was used to feedback control the output power of semiconductor laser. The system was constructed in the Matlab Simulink module, and the simulation was carried out under the same input signal. The control effects of the second-order Tornambe controller and the proportional-integral-differential (PID) were compared in the running process of system. The results show that the time constant of CO1-K thermocouple measured by PID controller is 456.2ms, while that measured by Tornambe controller is 284.6ms. The second-order Tornambe controller can effectively shorten the time of the thermocouple temperature balance. Moreover, it is more convenient to set the parameters of the controller structure, which has strong practical value.