The objectives of our research were to observe the physiological responses of construction workers during hot summer and identify the worker heat tolerance level.A total of 10 workers were selected randomly from a building construction site in Shapingba district,Chongqing.Environmental parameters together with worker physical responses were collected.Moreover,based on ISO 7243,ISO 9886,ISO 8996 standards,worker metabolic rate was calculated using heart rate and also calculate WBGTeff.In the studied constructed site,there was not any specific working schedule for workers.Workers consciously avoided work during the hottest time of a day(appx.11 AM to 4 PM).Due to avoid direct sun exposure workers did not feel so fatigue,though in some cases WBGT was higher than the normal limit and sometimes with a high workload.Workers heat tolerance level was found to be good because all of them were local people and acclimatized with the hot weather for around 10 years and most of the worker define their work as a moderate work.During resting time worker heart rate range was 60-90 bpm,only one has 99 bpm and that indicate their good physical fitness.In this experiment natural wind and artificial wind(fan)was used as cooling methods at the end of the work.In these two cooling methods showed different results in case of decreasing skin temperature at 15min resting period.In fan condition Skin temperature start to decrease within 2-3 mins.and not to increase but in natural ventilation the result(skin temperature)was fluctuated.In case of,Heart rate in both condition showed almost similar result,it decreased around 15-20 bpm within 2-3 mins.and then maintain a certain level.During the working period,all the worker felt thirsty due to hot weather,they drank freely but they did not need any long-time break except lunch break.