Based on NCEP reanalysis daily data during 1979–2018, the spatio-temporal evolution of the 10–30-day atmospheric intraseasonal oscillations (ISO) at mid-high-latitude Eurasia and its effect on the European blocking frequency are investigated. The co-effect of the blocking and ISO on extreme hot event frequency is also investigated. The ISO exhibits two modes, that is, the eastward and westward propagating modes. During the eastward (westward) propagating mode, the northwest-southeast tilted quadrupole (east-west dipole) quasi-barotropic geopotential height anomaly coupled with the air temperature anomaly at the troposphere propagates southeastward (westward). Phase composite shows that, during both modes, the mid-high-latitude low-frequency Rossby wave trains significantly affect the frequency of the European blocking during the propagating journey. The most frequent European blocking appears in phases 6–7 (5–6) during the eastward (westward) mode which is referred to as E-P67 (W-P56). During E-P67 (W-P56), if there is no blocking, western Europe, the eastern European plain, the Ural Mountains, and northeast plain of China (Europe and the Ural Mountains) are respectively controlled by quasi-barotropic + – + – (+ –) height anomalies, resulting in significantly positive frequency anomalies of extreme hot events over western Europe and the Ural Mountains (Europe), and negative ones over the eastern European plain and northeast plain of China (Ural Mountains). If blocking occurs, During E-P67, the positive height anomaly intensity over western Europe increases significantly, and the positive or negative ones over the Ural Mountains, the eastern European plain and the northeast plain of China weakens. Meanwhile, a negative height anomaly appears south of Europe, leading to a negative extreme hot frequency anomaly; during W-P56, both the positive and negative height anomalies are intensified, and a positive and a negative height anomaly respectively appear over northeastern plains of China and south of Europe, respectively decreasing and increasing the hot events in the two regions. So, during E-P67 and W-P56, the European blocking increases (decreases) the frequency of extreme hot events in Europe and northeast plains of China (south of Europe and the Ural Mountains). Therefore, European blocking activities significantly regulate the effect of the two propagating ISO modes on the extreme hot events over the middle and high latitudes of Eurasia.