Abstract: Fine classification of Climate standard period,for 1961-1990,1971-2000,1981-2010,and 1991-2020,is adopted to calculate the extreme heat threshold at each station over the Beijing-Tianjin-Hebei region during 1961-2023.For each decade,the corresponding Climate standard period is adopted,and the time series and spatial distribution of extreme heat events are obtained.Results show that:The southern part of the Beijing-Tianjin-Hebei region has the highest extreme heat threshold,followed by the central part,with the northern part being the lowest.Thresholds in all three parts exhibit an upward trend with the evolution of Climate standard period.The total station-days during 1961-2023 over the Beijing-Tianjin-Hebei region show an upward trend with the speed of 0.24 d·(10 a)^-1.Extreme heat events occured mostly in June during 1960s and 1970s,while they occured mostly in June and July in 1990s and backwards.Atmospheric circulation diagnosis of 17 extreme heat events in 1972,2002 and 2023,The result shows that the warm high at 500 hPa over North China,along with the westward extension of the West Pacific Subtropical High,constitutes the typical circulation pattern for extreme heat events in the Beijing-Tianjin-Hebei region.