Objective To determine the definitive upper limit for training with different intensities in heat-humid environment, so as to provide evidence for safe working in heat-humid environment. Methods Thirty male volunteers aged 18-23 years old who passed both health examination and physical agility test were selected from a total of 576 trainees.The body temperature, including 5-point temperatures on the skin, rectal temperature and mean body temperature calculated, were obtained before and after each training episode; the results were compared with previously reported.Then a regression equation on the mean body temperature was developed and point estimation was done subsequently. Results (1) We found that 35.83% of the subjects had a mean body temperature higher than the upper limit previously reported.(2) If ＾y was the mean body temperature, X1 was the temperature in environment, X2 was the humidity in environment, and X3 was the intensity of work, the regression equations was ＾y=14.247 68+0.604 67X1-0.018 29X2+0.343 53X3; and a table was developed according to related point estimation. (3) There were 11 person/times (2.49%) out of 441 person/times whose mean body temperature surpassed the dynamic upper limit according to the table. Conclusion The mean body temperature is related to the environment temperature, humidity and work intensity in the heat-humid environment.The table developed by point estimation of the regression equation may help to ensure safe working in heat-humid environment.