Abstract: Comprehensive index of heat stress(CIHS) was given to pay attention to the high temperature influence on fighter pilots, and to supply proof to take necessary protection to the pilots. According to the airport weather report thermal environment parameters of fighter cabin were estimated first, heat and mass transfer process was analyzed about thermal system concluding pilot, summer flying wear and the cabin environment, and changes of human body thermal physiological parameters were simulated, then the CIHS was calculated. The heat and mass transfer analysis software of the thermal system was developed. The CIHS estimation curve under a given weather was plotted. The high temperature cabin experiments show that calculated results about average skin temperature, core temperature and average body temperature are similar to the experimental results, they have same change tendencies, similar increments between initial and final values. The heat stress early-warning results are the same. The deviations between experimental and calculated results are less than 20%, so the estimation model is reliable and reasonable, can meet the application very well.