The present invention provides a back frame of a flat panel display device. The back frame includes at least two assembling pieces. The at least two assembling pieces are joined to form the back frame. The back frame further includes a bracing piece that is set in pawl mating engagement with the assembling pieces. The present invention further provides a backlight system. The back frame and backlight system of flat panel display device form a back frame through joining assembling pieces so that the structure of a mold for back frame is simple, the expenditure for the back frame mold is reduced, the material for the back frame is saved, and the cost of flat panel display device is lowered down. Further, through the pawl mating arrangement of the bracing piece and the assembling piece, the bracing piece of the back frame realizes fast mounting and removal.