ZrO2（3Y）encapsulated Al2O3 nano composite powders were prepared by heterogeneous nucleation combined with the liquid co-deposition method using pH buffer solution as precipitator.The synthesized powders were characterized with XRD and TEM.The results indicated that the isoelectric point of Al2O3 suspension shifted to acidic side and the absolute value of Zeta potential also increased when a dispersant was added into the suspension.At pH 9.56，the absolute value of Zeta potential reached the maximum and the suspension was most stable.The maximum yield of the precursor was obtained at pH 9.5 and the concentration of ZrOCl2and YCl3mixed solution 0.2 mol8226;L-1.There existed two phases，i.e.，α-Al2O3 and t-ZrO2，in the composite powders calcined at 600℃.TEM observation confirmed that nano ZrO2（3Y）particles with a diameter of 10 nm were formed on the surface of Al2O3 particles.