The effect of sintering temperatures on the interfaces and mechanical properties of the C_f/SiC composites was investigated. Owing to the poor sinterability as a result of low sintering temperature (l700℃), a very weakly bonded fiber/matrix interface was formed , which gave the composite poor mechanical property. On increasing sintering temperature to l800℃, a carbon-rich interface not only avoided the direct contact of the fibers with the matrix, but also made the fiber/matrix bonding desirable, so the composite achieved excellent mechanical properties. However, the composite sintered at l850℃ or higher temperature showed substantially degraded mechanical properties, which was mainly attributed to the improvement in the fiber/matrix interfacial bonding and deterioration in the properties of the fibers caused by the serious reaction between the fibers and the interphase.