Y There is a broad application of laser communication. This technology makes a great contribution to information exchanging between a station on ground and a satellite in space or between two satellites in space. Transceiver of space laser communication usually shares one optical path for compact, lightweight, low cost design. The most important thing is that the laser communication should have low wave aberration, low polarization loss and high isolation. Transmitting and receiving signals use one optical path, which makes negative influence on the isolation in system. It is a big challenge for engineers or designers to ensure the high isolation. The paper made a design about the key device in the transceiver, which was sensitive to isolation. The basic idea of this design was using the special structure style and optical material. It could eliminate stray light efficiently. It was proved that the process of manufacturing and assembling was not difficult. The device proposed in this paper could improve the efficiency and quality of laser communication. Moreover, the paper made mechanical simulation of device to prove that the device was safe.