Human thermal adaptation and its potential effect on indoor thermal environment design have driven researchers to explore the mechanism underpinning acclimatization.A large number of studies have verified human heat acclimatization and acclimation to temperature whereas few studies focus on the acclimation to humidity.To reveal whether people with short-term exposure have acclimation to extreme humidity in hot environments and how the acclimation affect people thermal perception,a comparative experiment with hot-humid(32℃-80%RH)and hot-dry(32℃-20%RH)was conducted in a well-controlled climate chamber,with both physiological measurements and psychological questionnaires.Totally 24 subjects were involved in the continuous 7-days repeated exposure to humid stimuli.Despite the non-significant difference of subjects mean skin temperature(MST)between two humidity levels,the results showed that the change rate of MST increased at the initial 30min during the 7-day exposure,indicating the rapid responses and thermoregulation to hot-humid stimuli after acclimation.The subjects blood flow,and sweating loss were both affected by humidity and heat acclimation.Subjects thermal perceptions were closely related to the physiological responses.The change trend of subjects thermal sensation was inconsistent with MST during the 7-day exposure,decreasing up to 0.5 under 32℃-80%RH.These findings demonstrated the heat acclimation differences to high and low air humidity through repeated short-term exposure,which can be reserved as a reference to indoor thermal environment design taking into consideration people long-term acclimatization to hot-humid environments.