Abstract: Using the ERA5 reanalysis data, this research is conducted on the onset timing of the Northern Hemisphere stratospheric polar vortex (NSPVO) during the seasonal transition of atmospheric circulation from summer to winter in the period spanning 1950 to 2022. The circulation differences and tropospheric precursor signals between the early- and late-NSPVO are explored, as well as the physical mechanisms that influence the early- and late-NSPVO. The results indicate that the mean date for NSPVO at 10 hPa is August 27th. The maximum range of the establishment time spans 24 days. The average time discrepancy between the 17 early- and 13 late-NSPVO years amounts to 12 days. In the early-NSPVO years, the Northern Hemisphere baroclinic annular mode (NBAM) in the troposphere at middle and high latitudes anomalously strengthens from the second week before NSPVO. In the early-NSPVO years, starting from the second week before NSPVO, there are there are precursors of anomalous strengthening of the Northern Hemisphere baroclinic annular mode (NBAM) in the troposphere in middle and high latitudes. Correspondingly, an anomalously enhanced Rossby wave train appears over the Asia-North Pacific tropospheric region, where the wave 4 of the Rossby wave dominates the anomalous upward propagation of wave activity flux (WAF), promoting the enhancement of the zonal-mean NBAM during this stage. Under the influence of the abnormality of this Rossby wave, in terms of the dynamic effect, the eddy west wind momentum flux anomalously converges outside the polar region, the eddy west wind momentum flux anomalously converges outside the polar region, prompting the acceleration of west wind. This acceleration process, with a maximum value exceeding 0.4 m s-1 day-1, evolves from outside the polar region toward the pole. However, this influence is mainly confined to the stratosphere and troposphere below 100 hPa. In terms of the thermodynamic aspect, the eddy heat flux anomalously converges and heats outside the polar region and above 100 hPa, with the maximum value exceeding 0.1 ℃ day-1 and it develops from the lower level to the upper level. The increase temperature gradient between the inside and outside of the polar region promotes the west wind anomalies into the middle and upper stratosphere through the thermal wind mechanism. Under the combined effect of the two aspects, within the week before NSPVO, the stratosphere west wind below 10 hPa enhance by more than 2.5 m s-1 near 70°N, resulting in the early-NSPVO. But if the regional Rossby wave is abnormally weakened in the early stage, NSPVO will be postponed.