A squall line storm that stroke Guangxi severely in 27-28 March 2013 was traced and alerted based on various observation data collected by conventional meteorological radar, and automatic meteorological stations, etc. This paper particularly analyzes the large scale circulation weather background, the characteristics of radar echo and formation mechanism of gale. The results show that this squall line is caused by the cold trough of high altitude and high pressure of ground. The good thermal and dynamic conditions over Guangxi are demonstrated on graphs of equivalent potential temperature and T logp. Initial convection is triggered by the ground convergence line. Surface pressure field of matured squall line has the mesoscale features including thunderstorm high, depression before and after the squall. Disastrous weathers such as gale of squall usually appear in the area of big values of barometric gradient and the split part of squall line before ground high pressure. On the other hand, the information of radar, including midaltitude radial convergence (MARC), reflectivity core and middle level greatest speed gradually decrease and the transition of the low level wind show vertical wind profile chart, which could be well in indicating ground wind. Drag effect of precipitation particles and the fast moving squall line have certain effect on generation and growth of ground gale.