The present invention provides a reflector plate and a backlight system. The backlight system includes a reflector plate and a back frame and the back frame carries the reflector plate. The back frame includes at least two primary assembling pieces, the at least two primary assembling pieces being joined to form a main frame structure of the back frame; and the reflector plate has a substrate containing a conductive fiber net for preventing electromagnetic interference. With the above arrangement, the backlight system of the present invention has a back frame having a simple structure, saving material for the back frame, and reducing the cost of the back frame. Further, the present invention integrates a conductive fiber net in a substrate of a reflector plate for preventing electromagnetic interference so that the reflector plate provides two uses of being a reflector plate and also realizing prevention of electromagnetic interference to thereby allow a backlight system or device that uses a joined back frame of the present invention can achieve the purpose of preventing electromagnetic interference with an easy manner and thus further reduce the manufacturing cost of backlight system.