Abstract: By using the shallow-water equations and WKB methods,the stability and development of the inertia gravitational waves are discussed in effect of the vertical shear of basic flow and the topo graphy with west-east direction.A ccording to the conclusions,the relationship between squall line's varying and the wave's development are tried to illustrated,which happened in the area of Beijing-Tianjin-Hebei on June 21,1992.It may provide a few thinking s for forecast the squall line.