An extreme cold wave event is analyzed on the isentropic potential vorticity (IPV) with the FNL reanalysis data from 1 Jan to 31 Jan 2016. The result shows that high potential vorticity (PV) was resulted from the splitting polar vortex, and the blocking of the front low PV and the proceeding northward moving of the rear low PV strengthened the meridional exchange of the PV. The high PV air continuously moved from the polar to the south, making the main body of the high PV continue to strengthen, and meanwhile, the high vortex also transported downward from the troposphere. The cold wave, which included three strands of cold air, developed from the upper to the bottom, settling in the north side of the upperlevel jet. In the southern tip a sinking airflow was most exuberant, which resulted from its interaction with the upperlevel jet. The sinking of the strong cold air made the cold wave influence the South China. As the high PV transmitted towards the south area, the low vortex system developed rapidly in the highlevel troposphere. When it moved to the eastern China, The East Asian Trough deepened rapidly, and finally induced the outbreak of strong cold air behind the trough. On the other hand, in the process of high PV transportation, the rear strongly sinking movement occurred to render the rapid development of the cold high on the ground and lead to the outbreak of cold wave weather.