To develop the fracture mechanics of ceramics, two types of cohesive crack models are investigated. Type A is a model which treats the bridging zone as a fictitious crack with cohesive stress distribution in which the crack develops when the crack tip stress intensity factor Ktip reaches Kup.c. Type B is a model which treats the whole fracture process zone as a fictitious crack with cohesive stress distribution. In contrast to type A. cohesive stress is distributed such that Ktip=0 and the crack will develop when the stress at the crack tip reaches σc. Numerical investigations for sample problems reveal that though both types of models are reasonable as mathematical models, it is difficult to determine the values of the parameters of the distribution function of cohesive stress for the type B model.