Abstract: Using a π-coordinate.given as equation(1),we derived a 3-layer model in which the motion of the troposphere and stratosphere is discribed.From the solutions of the linearized equations,the dynamical control and the steady perturbations produced by topography and heating are discussed.It is found that the topographic and thermal forced waves with zonal wave number 1-3 are able to penetrate into the stratosphere.The phase of the mountain waves is vertical but the heating waves tilt westward with increasing height.Both orography and heat sources are important in explaining the mean flow pattern in the stratosphere,but the tropospheric and stratospheric heating play the dominant role on the formation of Aleutian high at 30 mb.The large amplitude of the forced perturbation in the stratosphere is mainly due to the very small air densiy.