Using conventional survey, ground intensive observations, numerical pr ediction product T213 and FY-2c/2d infrared satellite cloud image, synoptic-dyna mical diagnosis and mesoscale analysis are carried on gale and strong sandstorm process initiated by squall line on May 2, 2008 in east of Hexi corridor. The re sults show that strong storm initiated by squall line produced the strong sandst orm. East of Hexi Corridor is in instable atmosphere stratification. Large scale circulation background is provided by stepped short wave trough of 500 hPa for squall line. Deformation field of 700 hPa is triggering system of squall line. G radient of pressure and temperature before and after cold front is enlarged by d evelopment of ground thermal low pressure, by whichthermal energy stability condition is provided for convection development. Upper air jet stream has vital role for production and development of squall line.