GO/Boron carbide (GO/B4C) composite powders were prepared by ball-milling and atomizing granulation. Reduced GO/Boron carbide (rGO/B4C) composites were obtained by vacuum hot pressing at 2 100 ℃ under the pressure of 30 MPa. The surface phase and mechanical properties of the composites were analyzed by SEM, TG and XRD, three-point bending method and drainage method. The effect of GO dosage on the bending strength and fracture toughness of rGO/B4C composites was studied. The results show that the uniformly mixed GO/B4C composite powder can be obtained by gradually adding the stable and dispersed GO/water suspension to the B4C slurry during the ball milling process. The bending strength and fracture toughness of rGO/B4C composites, in which the GO content is 1.5%, are 535 MPa and 5.2 MPa · m1/2, respectively, 72.6% and 136% higher than those of B4C ceramics. It is beneficial to the application of boron carbide ceramics in military protection field. The toughening mechanism of rGO/B4C composites was explained from the aspects of graphene pulling, crack deflection and bridging. This will allow future researchers to further investigate the toughening effect of GO and it is also conducive to its large-scale industrial production.