Abstract: 3Y-TZP ceramic was treated under atmospheric pressure and 100℃ boiling water for 0~100 hours. Friction and wear properties of aged 3Y-TZP were tested under 120 N load, 0.42 m/s sliding velocity and distilled water as lubricant. The results indicated that increased aging time decreased both hardness and bending strength of 3Y-TZP ceramic. The friction coefficient of aged 3Y-TZP ceramic decreased firstly and then increased while wear rate of 3Y-TZP increased as the aging time was prolonged. The main wear mechanism of no-aged 3Y-TZP was ploughing and plastic deformation. The worn surface of 3Y-TZP ceramic after 50 h aging was controlled by plastic deformation and microfracture. A transition of wear mechanism occurred because severe wear was observed for 3Y-TZP ceramic. After 100 h aging, fracture became predominant on the worn surface.