This paper describes the method for strength reliability evaluation of ceramics with machining damages and the prediction of the life of PSZ ceramics with thermal cracks caused by laser heating. The stress intensity factor of a four point bending model with machining damages is analyzed concerning with the number of cracks and crack density using finite element method. It is necessary to know the interactive interference of cracks within ten times area of each crack length in order to obtain the stress intensity factor of the crack tips which lead to failure. Also the crack growth parameter m and C of PSZ ceramics with the thermal crack damages are calculated from approximate equation of stress intensity factor in the machining damage model. As the result, it is found that the experimental results of fatigue test of the specimen with crack damages caused by laser heating agrees with the life predicted from analysis