Abstract: Four snowstorms in southern China are selected, and the ERA-Interim reanalysis data are used to derive the eddy potential enstrophy equation from the quasi-geostrophic vorticity equation, and to study the development of the trough during the snowstorm from the perspective of wave.The results show that the appearance of the trough is extremely important to the development of the snowstorm, and the wave-mean interaction has an obvious effect on the movement of the trough.The positive and negative effects in the bottom and front of trough respectively make the trough bottom appear positive and the trough front appear negative, thus making the trough move eastward or the horizontal trough turn vertical, which is conducive to the outbreak of cold air to the south and the generation of snowstorm in the south of China.