Strengthening and toughening mechanisms in composite ceramics is complex. A change in a single parameter induces multiple property variations. The multiple changes in properties are often incompletely represented in theoretical models. This incompleteness in the parameter chosen fails to explain the mechanism of failure in composite ceramics. The exponential toughness function is used to represent the pull-out toughening mechanism, which dominates the crack growth resistance curve(R-curve). The strengthening-toughening model is established based on the Mori-Tanaka method(M-T method). The influence of inherent defects on toughness function and strength is analyzed by using this model. The theoretical result is compared with the experiment data. This model exactly reflects the change in strength. The theoretical result indicates that defects change the toughness function. Moreover, micro-cracks increase toughness size ac, and the strength of crack instable extensions acutely decreases as defect content increases. This presented model establishes the relationship among the important mechanical parameters of defect, strength, elastic modulus, and the R-curve. Strengthening and toughening mechanisms in composite ceramics is complex. A change in a single parameter induces multiple property variations. The multiple changes in properties are often incompletely represented in theoretical models. This incompleteness in the parameter chosen fails to explain the mechanism of failure in composite ceramics . The exponential toughness function is used to represent the pull-out toughening mechanism, which dominates the crack growth resistance curve (R-curve). The strengthening-toughening model is established based on the Mori-Tanaka method (MT method). The influence The theory result is compared with the experiment data. This theory result is compared with the experiment data. Moreover, the micro-cracks increase toughness size ac, and the strength of crack instable extensions acutely decreased as This presented model establishes the relationship among the important mechanical parameters of defect, strength, elastic modulus, and the R-curve.