A heat dissipation system used for a communications device is disclosed, where the communications device includes a chassis, a network board, a service board, a backplane, and a high-rate cable; the chassis is configured to house the network board, the service board, the backplane, and the high-rate cable; the backplane is vertically inserted in a middle part or a middle rear part of the chassis, and parallel to a front side of the chassis; the service board and the network board are parallel and are connected to a front side of the backplane; the high-rate cable is connected between the network board and the service board on a rear side of the backplane; and the heat dissipation system further includes multiple fans that are installed in an array form on a rear side of the chassis, and an air vent that penetrates through the backplane.