We present a numerical model to simulate the damage and fracture process occurred in ceramic materials under thermal shock conditions. In particular, the variational principle is applied to gradient damage analy-sis in the establishment of the numerical model. The experiments on quenching tests of circular specimens are used to validate the efficiency of the model, proving that the proposed model is capable of reproducing faithfully the entire damage-fracture process of the ceramic specimens. Moreover, influences of different physical parameters are examined and discussed. We find that an internal length scale parameter, which can be considered as a material parameter, plays an important role in the entire fracture process.