Abstract: This paper presents the fracture toughness of theeutectic ceramic composite which is mainly composed of eutectic ceramic rodswith random size and orientation. Firstly, on basis of the microstructure,considering the boundary slip of eutectic rods, the cracking stress of theeutectic ceramic composite is determined. When the applied tensile stressequals to the cracking stress, the crack will grow. Secondly, we imaginethat the load carried by the eutectic ceramic rods in the crack wake willproduce a crack-closing force. It will reduces the stress intensity in frontof the crack. The bridging toughening mechanism of eutectic rods isconstructed. Thirdly, the pull-out work is given by the integral of thefrictional force over the pull-out length. The pull-out toughening mechanismof eutectic rods is obtained. And lastly, based on the bridging tougheningmechanism and the pull-out toughening mechanism, the enhanced toughnessscales with the inherent matrix toughness, and the theoretical formula offracture toughness of the eutectic ceramics composite is determined. Theresult shows that the fracture toughness of the composite is dependent onthe aspect ratio of eutectic-rod.