The present invention provides a back frame of flat panel display device, which includes primary assembling pieces and secondary assembling pieces; the primary assembling pieces are of a number of at least two, the at least two primary assembling pieces being joined to form a main frame structure of the back frame; the secondary assembling pieces are arranged inside the back frame and joined to the back frame; some of the primary assembling pieces and the secondary assembling pieces are of first density and first strength and others are of second density and second strength; the first density is greater than the second density and the first strength is greater than the second strength. The present invention also provides a method for manufacturing a back frame of flat panel display device and a backlight system. The back frame, the method for manufacturing back frame, and the backlight system have a back frame mold that is of a simple structure and can reduce the expenditure of the back frame mold, and can also save the material used for back frame so as to lower down the cost of flat panel display device.