Fiber eutectics and transformation particles composite ceramic possessed good strengths and creep resistance. It is mainly composed of fiber eutectics with random orientation and transformation particles. First, on basis of the strong constraining effect of the microstructure in fiber eutectics, the micromechanical stress field in fiber eutectics is determined by shear stress that develop between the fiber- inclusion and matrix is obtained. Then, the stress concentration duo to the dislocation pileup on the fiber- matrix interphase is analysised, and the maximum stress in matrix is obtained. Letting maximum stress in matrix equaled to theoretical strength of matrix, the micro strength formation of fiber eutectics is gotten. Finally, considering random orientation and length of fiber eutectics, the macro mechanical strength model of fiber eutectics and transformation particles composite ceramic is built. Result indicates that the fracture strength of composite ceramic has obvious size dependence: the fracture strength of composite ceramic will increase as the diameter of the fiber inclusion in fiber eutectics decrease.