Abstract: Crack propagating process in a Ce-TZP ceramics was in-situ observeed in TEM. It was found that the crack propagating process in this ceramics, similar to that in some metal materials, was microcrack nucleation ahead of main crack tip, microcrack growth, then main crack connecting with the micro one and propagating forward. The martensitic transformation of zirconia, induced by crack tip stress field, was observed in the vicinity of crack. Crack deflection was also observed in the ceramics. It was also found that the main crack tip was not sharp, it was a blunted crack.