Compared to the fluid motion field changes with time to slow time, it is reasonable for the assumption which exogenous does not change with time, when the atmospheric circulation as the fluid movement in the exogenous driven dissipative. Therefore, this paper discusses forcing the disturbance effect of positive pressure and without divergence of system dynamic equations of atmosphere, neglecting the topography and β effect. For linear systems, the equilibrium is a saddle point structure. At this time, changes in external forcing will cause change of the structure of the system. The topological structure of the system does not change, still for three dimensional saddle point structure, when the external force to the critical point. However, invariant subspace and unstable dimension of the invariant subspace will change. When the external source force tends to zero, the system from unstable will turn to stable state. At this time, the new steady bifurcation occurs, and the saddle point structure of before into stable node structure. For nonlinear systems, do not affect the structure of positive pressure and without divergence of atmospheric system, when the external forcing is small enough. In the vicinity of the real equilibrium, there is a stable local invariant submanifold and unstable local invariant 3D saddle submanifolds invariant manifold structure. Finally, based on the saddle point structure is difficult to integral characteristic, the structure of solutions near the equilibrium point is given, through used to integral method.