Abstract: Yttrium oxide powder was prepared by ammonia-oxalic acid two steps method. The cental particle size (D₅₀) was controlled to be 1.00~2.00 μm with good dispersibility. The effects of precipitant concentration, material concentration, reaction temperature, feeding rate and pH on the medium particle size of yttrium oxide powder were studied. Laser particle analyzer, BET instrument and scanning electron microscope were used to analyze the particle size and specific surface area of yttrium oxide powder. The results show that when the concentration of ammonium hydroxide is 1.0 mol/L, the mass concentration of oxalic acid is 10 %, the dropping speed is 20 mL/min, the temperature of oxalic acid solution is 80 ℃, the pH of the solution precipitated by ammonium hydroxide is 7~8 and the pH of the solution precipitated by oxalic acid is below 1, the central particle size (D₅₀) and specificsurface area of the prepared yttrium oxide powder are controlled to be 1.00~2.00 μm and 3.2~13.3 m²/g by adjusting the concentration of yttrium nitrate in the range of 0.4~0.8 mol/L.