Abstract: The two-dimensional gimbal of the space laser communication terminal is a critical component to establish high precision laser communication links both between satellites and between satellite and ground stations. The performance of its U-shaped frame structure affects directly the stability and measurement precision of the gimbal system. To meet the strict requirements at the payload launch phase and the harsh space environment, an optimization design scheme for the U-shaped frame structure utilizing aluminum silicon carbide (Al/SiC) composite material is presented in this paper. The scheme comprehensively considers material properties and structural layout, analyzes and optimizes 11 typical size parameters of the U-shaped frame, and achieves lightweight and high rigidity of the structure. The findings demonstrate that the thickness of the supporting end and the slope of lateral ribs of the U-shaped frame are the key factors affecting its weight and the first order fundamental frequency, and the optimization design of U-shaped frame structure has resulted in 25.03% reduction in weight and an increase of 85.48 Hz in the first order fundamental frequency. The mechanical vibration test confirms that the overall performance and reliability of the two-dimensional gimbal system have been significantly improved.