Abstract: In this paper linearized Boussinesq form equations with y direction basic flow are investigated by means of WKBJ method. A wave action density and the equations which describe the changing of wave parameters are obtained. The propagation and development of inertia-gravity wave packet are discussed. In addition, the ray tracing method is used to discuss the influene of nonuniform stratification on the propagation of wave packet. The main conclusions ares A) The downstream propagating waves from the jet axis to either side of the jet are amplified, while the upstream propagting waves are weakened. (B) when the sources emitting the wave packets are located far away from the jet axis, the downstream propagating waves from the sources on both sides to axis are weakened, while the upstream propagating waves are amplified. (C) the area of small stratificaton or area with precipitation attracts the energy of inertia-gravity wave and then the convection and storm are triggered off and activated.