In the context of global warming and rapid urbanization, urban wind-heat environment has become increasingly prominent. Although the identification of ventilation corridors has been well investigated, the impact of ventilation corridors on thermal environment remains unclear. Here, we use the single-window algorithm and circuit theory method to analyze the characteristics of land surface temperature (LST) and ventilation corridors in four megacities of China, so as to quantify the effect of ventilation corridors on thermal environment. Results show that circuit theory works well for identifying ventilation corridors. Moreover, we find that spatial distribution of ventilation corridors in one city is remarkably different from another. Interestingly, ventilation corridors, which consist of green spaces, waters, and roads, have a remarkable mitigation effect on thermal environment. LST of each city is mitigated by 2.39 ℃, 3.22 ℃, 2.11 ℃ and 2.60 ℃, respectively, and the cooling intensity in summer is better than that in winter. Thus, it is of great significance to arrange urban form and ventilation corridors to alleviate the impact of high temperature on urban residents.