Using the daily station observational data from the National Climate Center and NCEP/NCAR reanalysis data during 1951-2019, this paper analyzes the temporal and spatial distribution of the persistent extremely cold events (PECE) in northern Xinjiang and examines the interaction between stratosphere and troposphere during the occurrence and development of PECE events. The results show that on the interdecadal scale, the frequency of PECE in northern Xinjiang peaked in the 1960s, and gradually decreased since that time, means that the frequency of thePECE in northern Xinjiang is decreasing. In terms of spatial distribution, the center of the extreme value of both the frequency of PECE and the intensity of cold air locates along the Irtysh River Basin. During this period, both the stratospheric and tropospheric circulations have adjusted. First, a weak ridge was formed in Novaya Zemlya, leading to the upward propagation of the tropospheric planetary wave 1. After that, the stratospheric polar vortex over the Eurasian sector weakens from strong to weak state. Although the stratospheric polar vortex recovered and maintained its strength later, the upward propagation of tropospheric planetary wave was suppressed. Anomalously downward reflections of the tropospheric planetary wave occurred in Europe and Asia. The tropospheric polar vortex thus weakened, increased in area and move southward, causing a concurrent southward cold air. The cold air from the Arctic accumulates in front of the Ural High ridge, which is conducive to the strengthening and maintenance of the large inclined ridge. Meanwhile, the cold air at the surface forms an accumulation in the Central Siberia. Finally, accompanied by the strongly developed Siberian high pressure, the large tropospheric trough and inclined ridge lead the cold air to the south, which affected northern Xinjiang three days later.