Abstract: In this paper, a meso-scale analysis on a squall line process which swept Guangdong Province is operated mainly by utilizing self-recording data of the conventional surface observation network over Pearl River Basin. After surveying its orientatation, movements and the characteristic fluctuation of various meteorological elements during the passage of the squall line, it is concluded that this is a cold frontal squall line process. Based on the correlation between the daily maximum wind(V_M) occurrence time and the squall line passage, under some restrictive conditions, a few squall line activity days can be identified from historical data. The isochrones of V_M can be used to represent the appro ximate positions of the squall line. By analyzing their background fields, it is seen that all the six cases of squall line which moved eastward along Pearl River Basin initiated in front of an upper trough in the subtropical westerlies and most of them were associated with a surface front and low level southwesterly jet. The necessary instable stratifications resulted from the joint effects of lower tropospheric warm moist advection and mid-tropospheric cold advection. The propagating speed of squall lines were nearly equal to the 700 hPa average wind speed at Wuzhou and Guangzhou.