RBSC(Reaction Bonded Silicon Carbide) / graphite composites were fabricated by the method of melt Si in-filtration using a continuous reaction sintering process in SiC/graphite preforms. The SiC grain and residual graphite particle size in RBSC/graphite composites were increased with increased graphite particle size used in SiC/graphite preforms. The fracture strength of RBSC/graphite composites was 345-450 MPa. The frac-ture strength was reduced as increasing of the graphite size because of the formation of large abnormal SiC grains and residual graphites in RBSC/graphite composites. The fracture toughness of RBSC/graphite com-posites using graphite particle of 25$mu extrm{m}$ was 5.5 MP{{{{ {am }^{1/2 } }} The increased fracture toughness of RBSC/gra-phite composites seems to be due to the increasing in crack deflection by pull-out of residual graphites and integranular fracture of fine SiC grains around residual graphites