A flat plate bass loudspeaker comprising a flat plate diaphragm, at least three driving units and a housing. The driving unit comprises a voice coil unit and a magnetic circuit unit; the voice coil units are dispersedly coupled to one side of the diaphragm near the housing; mounting holes for accommodating and fixing the magnetic circuit units, and voice outlet holes penetrating through the housing are arranged on the housing; the number and position of the mounting holes are corresponding to those of voice coils attached to the spherical top of the diaphragm; and ratio of the total area of the voice outlet holes to the orthographic projection area of the diaphragm on the housing is in a range less than 0.9. The flat plate bass loudspeaker provided by the present invention can avoid the problems occurred in thick and heavy voice coils and excessive magnet performance.