Abstract: In order to improve the fracture toughness, reliability and the ability of resisting damage of the ceramic materials, appropriate multiple toughening mechanisms were introduced in alumina matrix ceramic materials. Phase transformation toughening can consume some energy, reduce the concentration of stress at the crack tip and prevent or delay the crack growth rate. When the distribution of reinforced phase is reasonable and the relative density is high, there are crack deflection and bridging forms in the crack propagation, which can weaken the crack extension power, and improve the fracture toughness of the material. The crack propagation was discussed based on extended finite element (X-FEM) method, which provides a new way for the analysis of the multiple toughening mechanisms of ceramic matrix composites.