Abstract: Using the pure NH₄Al(SO₄ )₂·12H₂O , ZrOCl₂ ·8H₂O and Y(NO₃ ) 3 as the starting materials , and theN H4 HCO₃ solution as precipitant , the ult rafine 3 Y-ZrO₂ / Al₂O₃ precursor was prepared by the liquid-phase precipitation method. The effect s of seeds and the calcination temperature on the properties of the powder were studied.The well-dispersible ZrO₂ / Al₂O₃ composite nanopowder with particles of 10 nm was obtained by calcining the precursor at 1000 ℃. The XRD patterns show noγ-Al₂O₃ andθ-Al₂O₃ form during calcination. The relative density andfracture toughness of specimen reach 98. 6 % and 7. 68 MPa·m^1/2 , respectively af ter sintering the green compact s at1550 ℃for 3 h.