On July 25, 2022, a widespread and extreme thunderstorm gale event suddenly struck Henan Province, with the maximum instantaneous wind force reaching Level 13 and the maximum instantaneous wind speed at 12 national meteorological stations exceeding the historical extreme values for the same period since their establishment. Based on multi-source data, including conventional observation data, FY-4 high-resolution satellite data, dual-polarisation radar data, and minute-level ground observation data, this study analyses the evolutionary characteristics and formation mechanisms of the extreme gale-force winds in this event. The results indicate: (1) The event occurred on the margin of the subtropical high under the background of an eastward-moving trough, which was jointly triggered by surface convergence lines and weak cold air. During the initial stage, strong radiative warming occurred at the surface in the afternoon, combined with the development of warm and moist advection in the lower atmosphere overlapped with the upper-level cold trough, forming a strongly thermally unstable stratification. The upper-dry and lower-moist structure was conducive to the occurrence of thunderstorm gales. During the development and maintenance stage, the eastward movement of the trough led to a significant increase in dynamic lifting, vertical wind shear, and carrying layer wind, which was conducive to the maintenance of gales. (2) This extreme gale event exhibited three distinct stages: In the initial stage, small bow echoes formed by the forward propagation of scattered convection in northwestern Henan, with localised extreme gales first occurring at the rear of these echoes and near supercell storms. During the development stage, the system gradually organised into linear convection in central and western Henan, with extreme gales concentrated in the regions near the apex of the bow echo embedded in the linear convection and the strong divergent regions on its rear. In the maintenance and weakening stage, the linear convection evolved into a larger-scale typical bow echo in central and eastern Henan, with extreme thunderstorm gales appearing sporadically near the locations with the maximum curvature of the bow echo and the hook echoes. Mesocyclones, γ-mesoscale vortices, low-level gale zones, deep radial convergence, and areas of low differential reflectivity factor (Z_DR) and low specific differential phase (K_DP) had certain indicative significance for the early warning of extreme thunderstorm gales. (3) Strong downdrafts, downward momentum transport, cold pool density currents, and topographic effects were the primary causes of this extreme thunderstorm gale event. In the initial stage, negative buoyancy was the main factor leading to strong downdrafts. During the development stage, the combined dynamic forcing of negative buoyancy, precipitation drag, and γ-mesoscale vortices dominated the formation of strong downdrafts, superimposed with the synergistic effect of downward momentum transport, cold pool density currents, and downdraft divergent airflow, leading to an increase in the intensity and expansion of the extreme gales. In the maintenance and weakening stage, downward momentum transport and cold pool effects were predominant. Additionally, the convergence lines caused by topography significantly promoted the organised development of the convective system, while the superposition of local trumpet-shaped and narrow-tube terrain effects further enhanced the extremeness of near-surface wind speeds.