To enhance the personalized thermal protection effectiveness for workers exposed to hot environments and clarify the individualized protection strategies with different body types, this study investigated the physiological and perceptual responses with different BMI in hot environments to explore individual thermoregulation capacity during heat exposure. First, two hot environments were set in a climate chamber, including neutral ((25.1±0.4)℃, (52.8%±1.9%) Relative Humidity(RH), 0.1 m/s) and high temperature ((35.0±0.5)℃, (50.0%±2.9%) RH, 0.1 m/s). Twenty male participants were recruited and divided into two groups: overweight (BMI ≥ 24) and underweight (BMI < 18.5). Second, participants were initially seated in neutral environment for 10 minutes, then performed alternating cycles of exercise and recovery in the hot environment. Physiological and perceptual responses parameters were recorded during the human trials. Finally, the regulatory mechanism of BMI on thermal responses and the extent of its impact were evaluated by analyzing the differences in subjective and objective indicators between the two groups of subjects. The results indicated that the two groups significantly (p<0.001) differed in core temperature, with the increase of 0.55 ℃ for the overweight group and 0.46 ℃ for the underweight group. The mean skin temperature of overweight and underweight participants increased by 4.2 and 2.9 ℃, respectively, indicating that overweight individuals were more sensitive to high temperatures. The total sweat rate and heart rate of overweight participants were significantly higher than those of underweight participants, while no significant difference was observed for heart rate between the two groups. Differences in BMI led to statistically significant differences in perceptual responses parameters (p<0.05), not only affecting the intensity of thermal responses but also inducing differences in the patterns of regulatory mechanisms. Therefore, individualized thermal protection strategies should be formulated based on body type characteristics.