The processing and mechanical behaviors of Al 2 O 3 -xwt.%SiC (x=1, 2, 5, ASx) nano-composites prepared by the in situ synthesis of SiC from polycarbosilane (PCS) were investigated. The composites were densified by hot pressing. The microstructure and mechanical properties of the sintered composites were analyzed. The results showed that a fully dense structure was obtained when a few nano-SiC were doped and that the fracture toughness and strength were highly improved compared with those of monolithic Al 2 O 3 . The fracture toughness reached 5.1MPa m 1/2 in AS2 composite. The maximum flexural strength was 516MPa obtained in AS1 composite.