Based on the conventional observation data,Doppler radar observation data,wind profiler radar data and NCEP/NCAR reanalysis data,a squall line event occurred in Guangzhou Baiyun airport terminal area on 30 April 2013 was analyzed and simulated.Results show that the weather event is caused by the east movement of the upper trough,which drives weak surface cold air southward.The shape and intensity changes of squall line simulated by WRF(Weather Research and Forecasting) model are quite in agreement with the observations.There are obvious tilted updraft in the squall line.In the stage of development,there are updraft in the whole squall line,while in the mature stage,the updraft above 600 hPa and the downdraft in middle and low levels as a result of drag effect of heavy rain.There are obvious surface cold pool and thunderstorm high during the squall line process,and there is an obvious correlation between intensity change of squall line and change of cold pool.In the stage of development,the thunderstorm high locates in the low and back parts of the whole squall line,while in the mature stage,the positive pressure change in the low part and the negative pressure change in the back part are symmetrical.