Geothermal environment is easily formed due to alternating uplift or subsidence of continental plates in the world. In this special environment, tunnel engineering activities will inevitably encounter the problems of high temperature and thermal damage. In the construction process of high geothermal tunnel, high temperature has a great impact on the comfort of workers. This paper is based on the extra-long highway tunnel with the highest temperature of 88.8 °C in China. Through literature research, field monitoring, numerical simulation, theoretical calculation and other means, this paper investigates evaluation system of worker comfort during construction in high geothermal and deep buried tunnel. The comfort of workers is mainly affected by geological conditions, construction conditions, geographical environment conditions and thermal insulation and cooling measures, including 19 impact indicators, such as rock temperature, buried depth, excavation method, thermal insulation layer, ice block, ventilation. Based on the impact indicators, the AHP-Extenics evaluation system is established for worker comfort. The results show that the worker comfort level is level I in Nige Tunnel after adopting thermal insulation and cooling measures. On the whole, the worker can work comfortably. Finally, based on the AHP-Extenics evaluation system, a design process of worker protection is established to ensure that the comfort level of worker meets the requirements.