The present invention provides a back frame of flat panel display device, which includes at least first and second primary assembling pieces. The at least two primary assembling pieces are joined to form the back frame. The primary assembling pieces have a snap-on engagement section, and the snap-on engagement section mates a front frame of the flat panel display device. The present invention provides a back frame of front panel display device, a backlight system, and a flat liquid crystal display device that form a snap-on engagement section on a primary assembling piece to mate a snap-on engagement of a front frame of the flat panel display device to fix the front frame of the flat panel display device and also to allow of easy disassembling of the flat panel display device.