Plasma pattern formation in 110 GHz microwave air breakdown is investigated by numerical solution of fluid-based plasmas equations coupled with the Maxwell equations. It is found that the filamentary plasmas are observed at high pressure, the filamentary plasmas transit to diffuse plasma at medium pressure, and the diffuse plasma is obtained at low pressure. The plasmas region propagates toward the microwave source. The distribution of initial electrons influences merely plasmas pattern at first stage, but not final plasmas pattern. The movements in the directions parallel and vertical to electric field are different. Due to the strong electric field at the poles of the plasmas region, the plasmas are elongated in the direction of electric field, forming the filamentary plasmas at much low pressure in E plane.