Using the data of surface meteorological observation, regional automatic meteorological station observation, radar and satellites, and NCEP 1°×1° 6hour reanalysis, the formation mechanisms of a squall line weather process in the southern part of the Panxi area on 13 May 2018 is analyzed. The highaltitude trough gradually moved eastward to push the cold airflow to the east along the leeward slope, and then merged with the lowlevel warm air in front to form convection. The main trigger factor making the squall line weather process happen was the dewpoint front. The atmosphere around the squall line had the characteristics of dry at upper levels and wet at lower levels, high instability energy, strong vertical wind shear, large highlevel wind speed and the presence of an inversion layer before formation. The upper level jet stream and momentum downward transfer had a positive effect on the occurrence and strengthening of the squall line. The terrain had an effect on the formation of the squall line and the distribution of the weather phenomena.