The working principle of high energy laser systems is focusing the transmitting laser beam onto target while the target is tracked in a closed-loop using a fine tracking module, so that the target can be damaged or invalidated. In order to achieve this, an optical device with a co-aperture is designed for high-energy laser systems. The emitting system of this device is a two-stage beam expander consisted of an off-axis two-trans primary telescope module, a Galileo transmission telescope module for focusing, and a beam-feeding module. The receiver of this device is a long-focus optical system consisted of the same off-axis two-trans primary telescope module, an imaging module for fine tracking, and the same beam-feeding module, which is composed of a dichroic mirror, a fast mirror and other optical elements. Using an incoherent combination laser in space as laser source, we use optical design software in both the sequential mode and the non-sequential mode to design and simulate this device. The simulation results show that for the emitting system, the distribution of the spot at 0.5~5 km is obtained after the laser is modulated by different focusing quantities in the focusing telescope module. The RMS value of the laser wavefront is found to be better than λ/20 in the emitting system. In addition, the performance of the imaging optical system approaches the diffraction limit after optimizing, and the system transfer function is greater than 0.6 at 70 lp/mm. A prototype experiment is carried out to verify the correctness and rationality of this design. The results of this paper confirm that this optical transceiver possesses reasonable structure and reliable performance, which meets the engineering requirements of high-energy laser system applications.