Pressure and microwave power are the most important parameters during microwave breakdown in air and affect the self-organization plasma pattern structure and its propagation directly. In order to study the effects of pressure and microwave power, an effective-diffusion fluid plasma equation is solved together with Maxwell's equations, and the double grid method is also used to meet the different grid size requirement of plasma equation and finite-difference-time-domain for Maxwell's equations. The numerical results show that with lower pressure the plasma behaves as a more diffuse plasmoid instead of a well defined plasma pattern structure under higher pressure, and the increase of incident microwave power will lead to a rapid growth of the front propagation velocity and a well separated and sharp pattern structure, and the higher incident power also results in jump-like front propagation.