The present work focuses on the failure mechanisms that occur in melt-growth composite ceramics mainly composed of fiber eutectics with random orientation. First, the stress field of the melt-growth composite ceramics under a tensile stress was obtained. It can be visualized that tensile force is transmitted between oxide fiber eutectics by means of shear stress that develop along the interfaces of oxide fiber eutectics. Consider fiber eutectics having lengths smaller than the critical length. During the composite ceramics fracture, fiber eutectics do not fracture. The average stress of a fiber eutectic can be determined by the shear stress. Then, the probability of ending fiber eutectics and bridging fiber eutectics can be gotten by defining a critical ditrict βl. Finally, consider random orientation and length of the fiber eutectics. Composite ceramics failure by slip incompatibility. The strength model of the melt-growth composite ceramics is built. It is accordance with experiments.