Abstract: Low temperature (60-120 ℃) ageing behavior of Y-TZP/platy alumina composites in alkali solution was investigated by means of X-ray diffraction (XRD) and scanning electron microscopy (SEM). The bend strength and fracture toughness of the composites after ageing were measured. The results show that part of the tetragonal phase ZrO2 on the surface of the sintered body transformed to monoclinic phase ZrO2. The quantum of phase transformation in alkali solution increased with ageing temperature and pH value of the solution. The bend strength of the Y-TZP/ platy alumina composites after ageing slightly decreased,but the toughness of the composites changed a little.