Abstract: M40JB-C_f/SiC and T800-C_f/SiC composite's elevated temperature tensile strengths were tested with spindle-shaped and rectangular specimens. The tensile strength and tensile modulus were got after modifying the spindle-shaped specimen's strain formula. The elevated temperature tensile results showed that M40JB/SiC composite's tensile strength was 374MPa under 1300℃ and 338MPa under 1450℃, the tensile modulus was 134GPa under 1300℃ and 116GPa under 1450℃. Compared with the M40JB-C_f/SiC composites, the T800-C_f/SiC composites' tensile strength was 392MPa under 1300℃, higher than the M40JB-C_f/SiC composites, while the tensile modulus was 115GPa under 1300℃, lower than M40JB-C_f/SiC composite's. From the elevated temperature tensile test results, it was found that the composite tensile strength was correlative with the specimen's failure mode. When the failure happened at the effective part, the tensile strength values were higher than the values when the failure happened at the ineffective part, which were only 250MPa. The tensile stress-strain curves of M40JB-C_f/SiC composites showed non-linear-elastic fracture characters clearly of plastic materials, but the tensile stress-strain curves of T800-C_f/SiC composites were the linear curves.