Dynamic fatigue behavior of two kinds of Y-TZP ceramics was investigated at room temperature. The results showed that dynamic fatigue and slow crack growth behaviors exist in zirconias. Crack growth exponents of original and pre-cracked samples were obtained. Crack growth exponents of the two original zirconias are 15.60 and 21.00, respectively. Crack growth exponents of annealed pre-cracked samples are close to the original samples, indicating that the pre-crack experimental method is reasonable and effective. Because of the influence of residual stress indcued by indentation, crack growth exponents of unannealed samples are different from that of original samples. So residual stress should be removed.