Abstract: The downward propagation of circulation anomaly signals associated with stratospheric weak polar vortex events can significantly influence large-scale circulation in the mid-high latitudes of the troposphere, thereby modulating weather and climate variability. Understanding the factors and key processes influencing the downward propagation characteristics of these anomalous signals is crucial for the application of stratospheric signals in extended-range tropospheric forecasting. Based on the vertical evolution characteristics of the zonal wind anomalies averaged over 50°N–70°N, a total of 60 winter (November–March) stratospheric weak polar vortex events during the period 1952–2022 were classified into downward-propagating and non-downward-propagating events. Events that propagated down to 500 hPa (downward-propagating) accounted for approximately 53.3% of the total, with 43.3% propagating down to 1000 hPa. Differences in characteristics of the stratospheric polar vortex between the two event types primarily manifested as follows: relative to non-downward-propagating events, downward-propagating events were accompanied by stronger peak intensities and longer durations of circumpolar westerly anomalies, whereas differences in the morphology and position of the stratospheric polar vortex were not significant. Diagnostic analyses of planetary wave activity showed that the upward and poleward Eliassen–Palm (E–P) flux anomalies during the early stage of downward-propagating weak polar vortex events were generally stronger than those in non-downward-propagating events. This was attributed to weak westerly conditions in the mid-high latitudes of the upper troposphere during the early stages of downward-propagating events, leading to wave propagation environments more conducive to the upward propagation of planetary wave energy. This provides a dynamical explanation for why the intensity and duration of stratospheric anomalies in downward-propagating events exceed those in non-downward-propagating events. During the late stage of weak polar vortex events, the downward and poleward E–P flux anomalies associated with downward-propagating events were generally stronger than those in non-downward-propagating events. This was related to the wave propagation environment between the lower stratosphere and the middle troposphere that was more conducive to the reflection of planetary waves with zonal wavenumbers 1 and 2 (especially wavenumber 1), as well as to the weakening of the polar jet stream, accompanied by the strengthening of the tropospheric subtropical jet stream, which restricted a greater proportion of tropospheric planetary waves to mid-high latitudes. Anomalous wave reflections from the stratosphere to the troposphere, coupled with jet stream conditions in the troposphere that are conducive to planetary wave development, explain the late-stage downward propagation characteristics of such events.