The analysis is based on daily temperature data from 172 national basic meteorological stations in the Beijing-Tianjin-Hebei region, in conjunction with NCEP/NCAR second-generation reanalysis data, NOAA sea surface temperature data, and outgoing longwave radiation data.This study systematically investigates the spatiotemporal evolution characteristics of an extreme high-temperature event and reveals its formation mechanisms from multiple perspectives, including the influence of atmospheric circulation systems, antecedent sea surface temperature anomaly forcing, and radiative-convective conditions.The results indicate that: (1) In July 2025, the monthly mean maximum temperature in the Beijing-Tianjin-Hebei region exceeded the climatological mean for 27 days, with a maximum anomaly of 4.85°C. Spatially, both the anomaly of high-temperature days and the anomaly of mean maximum temperature exhibited a distribution pattern characterized by "low in the northwest and high in the southeast". (2) The extreme high-temperature event in the Beijing-Tianjin-Hebei region in July 2025 formed under the stable circulation background of an anomalously strong, northward, and westward Western Pacific Subtropical High. This was superposed by the forcing of antecedent warm sea surface temperature anomalies in the western Pacific and developed synergistically through the positive feedback mechanism of clear-sky radiation and subsidence warming. Specifically, the ridge line of the Western Pacific Subtropical High was located approximately 10 degrees of latitude north of its climatological mean, and its western extension point remained persistently westward. The warm and humid southerly airflow from low latitudes was significantly enhanced. Sea surface temperatures in the western Pacific region were anomalously high in the preceding period. Cloud cover over the study area was significantly reduced, and clear-sky radiation continued to intensify. Under the combined influence of these factors, the intensity and duration of the high-temperature event in the Beijing-Tianjin-Hebei region in July 2025 were further exacerbated.