The thermal environment increases the risk of thermal injury for persons under high temperature environment. A full understanding of the effects and hazards of the thermal environment on the human body is of great significance to improve the awareness of persons under high temperature environment and reduce occupational heat damage during work. The authors mainly review the thermal environment from aspects of the definition, mechanism of its influence on main functional systems of the human body, influencing factors of heat stress and progress of protection, so as to provide references for the identification and protection of heat-induced diseases for workers under high temperature environment.