The traditional traceable thermocouple dynamic calibration system uses CO2 laser as the light source, which has the characteristics that laser light energy distribution is not uniform , the adjustment of optical path is inconvenient and heated uniform of the sensors cannot be guaranteed. The light source of semiconductor laser had stable and uniform output light spot, but the divergence angle is large. In order to simplify traceable thermocouple dynamic calibration optical design, control the laser light path more convenient, and ensure the uniform heating of the thermocouples, the appropriate fiber optic and lens coupling are selected using Zemax software to improve the light path. The results show that the design greatly reduces the difficulty of light path adjustment, improves the efficiency of the laser, and provides high quality laser source for the traditional traceable thermocouple dynamic calibration system.