A mechanism to fix the new type of the pluggable optical transceiver to the host system is disclosed. The optical transceiver provides the screws, while, the host system has the face panel with a port and the rail system between which the optical transceiver is set through the port. In the present invention, the screw of the transceiver is fastened to the rail not the face panel, and the rail is precisely aligned with the electrical connector. Thus, the pluggable transceiver in the electrical plug thereof is exactly mated with the electrical connector of the host system.