Abstract: In this study, the heredity of yttrium oxide precursors prepared by the oxalic acid precipitation method was deeply discussed, aiming at optimizing its preparation process to obtain yttrium oxide materials with ideal particle size distribution. In the experiment, with high-purity yttrium oxide, hydrochloric acid and oxalic acid used as raw materials, yttrium oxide and its precursors were successfully prepared by accurately controlling the reaction conditions (acidity of yttrium chloride solution, oxalic acid concentration, precipitation direction, time and temperature, etc.). The products’ particle size, morphology and phase were analyzed by a laser particle size analyzer and X-ray polycrystalline diffractometer. The results showed that the best conditions for preparing large-particle yttrium oxide were 0.2 mol/L yttrium chloride concentration, 2 mol/L acidity, 1.5 mol/L oxalic acid concentration, forward precipitation for 2 hours, reaction temperature at 80 ℃, and aging for 6 hours. In addition, a key phase transition occurred in the aging process of yttrium oxalate, from Y₂ (C₂O₄) ₃ 6H₂O to YH (C₂O₄) 2H₂O, which had a significant impact on the particle size of yttrium oxide after calcination. By optimizing the aging conditions, the heredity of yttrium oxalate improved, but also the particle size of calcined yttrium oxide was effectively controlled to avoid excessive reduction, which provides an effective way to prepare high-performance yttrium oxide materials.