Abstract: Based on the daily average temperature data of 125 stations in Yunnan, the four paths of cold air entering Yunnan during 95 strong temperature-decreasing processes in winter from 1961 to 2020 are determined. The impacts of cold air along different paths on temperature-dropping in Yunnan and differences in atmospheric circulation are compared and analyzed. The result shows that the cold air along the northeast path has the severest impact on the temperature-dropping range and the widest spatial range of Yunnan. The easterly path has the highest frequency. The temperature-dropping ranges and impacting spatial scales of the easterly and northerly paths are close, while those of the southeast path are the weakest and least frequent. For the two days ahead of strong cooling day, the strongest are the intensity and area of positive height anomaly in the 500 hPa geopotential height field on the Eurasian continent, the intensity of the 700 hPa anticyclone anomalous circulation and the Siberian high of the northeast path, and the weakest are those of the southeast path, while between the previous two paths are those of the easterly path and the northerly path. The Eastern Asian trough at 500 hPa of the northeast path has the most obvious feature of transforming from horizontal mode to vertical mode. The trough bottoms at 500 hPa of easterly path and northerly path have deepened and moved southward, but the feature of transforming from horizontal mode to vertical mode is not as obvious as those of the northeast path. The trough bottom of southeast path is wider and broader. The subtropical high of the northeast path looks like blocks and has the smallest area, while the subtropical highs of the other three paths are banded, and the area of subtropical high in the easterly path is the largest. Both the northeast and easterly paths have strong negative sea level pressure anomaly areas near Japan, the cyclone anomaly circulations on the Korean Peninsula at 700 hPa are stronger, and the strong northerly airflow on the west side of the cyclone leads cold air into Yunnan. The cyclone anomaly circulations of the southeast path and the northerly path on the Korean Peninsula at 700 hPa are weaker, and so is the northerly flow on the west side of the cyclone. On the 200 hPa zonal wind anomaly field, the strongest are the intensities of positive and negative anomaly areas near the jet axis of the northeast path. The distribution of the easterly path along the jet axis is positive in the west and negative in the east. The intensities of positive and negative anomaly areas of the southeast path are the weakest, and the negative anomaly areas are mainly distributed in the north side of the jet axis. The negative anomaly areas of the northerly path are distributed in the north and south sides of the jet axis.