The composite materials TiN/3Y-TZP, 3Y-TZP doped by TiN with different contents and particle sizes, were fabricated through the same hot-pressing techniques. Compared with 3Y-TZP, the low temperature degradation resistance of TiN/3Y-TZP aged at the temperature from 170°C to 350°C in air for 50 h was investigated in virtue of XRD and SEM in the experiment. For TiN/3Y-TZP and 3Y-TZP, the maximum aging rate all occurs at 220°C. The addition of TiN can availably improve the low temperature degradation resistance of 3Y-TZP at different aging temperatures, but cannot change the relationship between the aging rate and the aging temperature. For TiN/3Y-TZP, the matrix particle size is the key factor responsible for its low temperature degradation resistance.