A communication system, which is applied to a space, includes a first transceiver and a communication device. The first transceiver is fixedly disposed in the space. The communication device is movable in the space. The communication device includes a base, a second transceiver, a detection circuit, an arm and a processor. The second transceiver is oriented to an orientation and configured to build a signal transmission with the first transceiver. The detection circuit is configured to detect a displacement or rotation of the communication device with respect to the first transceiver, in order to generate detection information. One end of the arm is connected to the base, and another end of the arm is connected to the second transceiver. The processor is configured to control an operation of the arm according to the detection information, in order to maintain the orientation of second transceiver directing to the first transceiver.