Abstract: The southeastern coastal areas are extensively influenced by the geothermal activities along the Pacific Rim. Especially during the excavation of deep-buried tunnels, the accumulation of heat flow in the enclosed space is likely to form a high-temperature and high-humidity environment, which adversely affects the physical and mental health of personnel and the safe operation of equipment. Therefore, based on the Lijiashan deep-buried high-temperature tunnel of the Wenling to Yuhuan high-speed railway, on-site monitoring of the temperature distribution of the surrounding rock and the structure as well as the wet and hot environment, and a comprehensive temperature and humidity evaluation index was used to evaluate the tunnel construction environment. The results show: (1) The high-temperature tunnel in the southeast coastal area is the result of the combined effect of geothermal heat and the heat released by the lining concrete. The temperature of the surrounding rock is 22.1℃, the temperature of the secondary lining can reach up to 58.6℃, and the maximum ambient temperature in the working area can reach 35.2℃; (2) Spraying water for cooling can reduce the temperature in the construction area by approximately 5%, but it also causes an increase of about 16% in humidity. The average humidity of the tunnel body during the day and at night is 75.3% and 87.5% respectively; (3) The evaluation of physiological comfort parameters for workers shows that the wet and hot environment during the tunnel construction process is always unfavorable. Reducing the temperature of the intake air can significantly improve the wet and hot environment in the construction area.