Abstract: In the paper a general conservation law of potential vorticity is obtained,the condition being that divergence of vector M=Gq+BΔΛF is zero, where G is the external source and F is the friction. The conservation laws of wave energy, action and enstrophy for Rossby waves are derived by using WKB approximation in a slowly varying basic flow and a variable stratification parameter, the conditions of conservation are that: (1) when the basic flow is independent of space coordinate the wave energy is conserved locally; (2) if the flow is independent of x, the wave action is conserved; (3) when the basic flow is of arbitrary slow variations, the wave enstrophy is conserved locally. Finally, the effect of topography is mainly of the slope of west-east direction and it causes only the variation of wave action.