A communication unit in a ring main unit has an optical cable termination box. The optical cable termination box is connected with an ONU data box. The communication unit is characterized in that the communication unit is also provided with a box body; the front of the box body is provided with an opening; the box body is internally provided with a separator plate; the separator plate divides the box body into an upper box body and a lower box body; the lower box body is provided with heat dissipation holes; the separator plate, the side wall of the upper box body and the side wall of the lower box body are provided with wire holes; the optical cable termination box is arranged in the upper box body; and the ONU data box is arranged in the lower box body. Since the optical cable termination box and the ONU data box are integrated in the box body, the communication unit and an automation unit in the ring main unit are separated, orderly wiring is achieved, and cases of misoperation in the maintenance process are effectively prevented; and since the ONU data box which is easy to generate heat is arranged in the lower box body having the heat dissipation holes, highly targeted effect is achieved, and good heat dissipation effect is achieved.