In order to contribute to the development of the joining technique of Cf/SiC, joining of SiC ceramic to high strength graphite was investigated. This joining has been successfully realized by reaction joining process using a preceramic polymer, polysiloxane, mixed with the active additive Al-Si powder as joining material. The weld strength is strongly affected by the technological parameters and the ingredient ratio (polysiloxane:Al-Si powder). The optimized factors have been obtained by orthogonal experiments, under which the achieved three-point bending strength of the joints is 96.8% of the strength of the welding base material graphite. The microstructure and composition of the weld zone were analyzed by SEM, EDX and XRD. The results show that the joining material has transformed into a densified interlayer with the thickness of about 15μm. Also, diffusion takes place in the interfacial area, which contributes to a sound interfacial bonding. The interlayer is composed of SiC, Al2O3 and Si.