The conventional observation data, NCEP/NCAR reanalysis data and Doppler radar data are used to analyze the squall line process happened in Guangdong during 30-31 March, 2014. The circulation background of environmental characteristics, unstable situation, vertical wind profile and Doppler radar echo evolution process are emphasized. Results show:(1)the squall line occurred in a stably maintained blocking situation of middle-high latitudes. The upper trough moving eastward from Sichuan basin and low vortex shear line are the main influencing systems causing strong convective weather of Guangdong.(2) Low-level jet vapor transportation, strong low-level moisture convergence and vertical wind shear, as well as dry upper and wet lower vapor vertical distribution provide necessary thermodynamic and dynamic conditions for the formation and development of the squall line.(3)There obviously exists gust front and weak echo channel at the strong stage of squall line. The strong cyclonic shear appears in the northern part of velocity map, and the weak anticyclonic shear is in the southern part. There is strong speed convergence in the vertex of bow echo. Sloping-downward cold air inflow is inside the back of squall line, and a warm air inflow climbing along the cold air is in the front.(4) Rear Inflow Jets(RIJ), sustaining for a long time in the top of bow echo back, plays an important role for the formation of bow echo and for the maintenance and fast moving of surface wind and squall line.