Abstract: Oxalic acid as a precipitating agent, preparation of Gd₂O₃ that center particle size D₅₀ is between 20 ~ 39μm by using positive precipitation way. The effect of rare earth feed solution initial concentration,oxalic acid concentration and precipitation temperature, aging time, burning temperature and dropping on the final product particle size has been analyzed through Malvern laser particle size analyzer and SEM. The results showed that: gadolinium chloride starting concentration 0.9mol/L, dropping rate of 1mL/min, precipitation temperature 60℃~70℃, oxalic acid concentration of 1mol/L, aging time 10h, ignition temperature 900℃, large particle Gd₂O₃ that center particle size D₅₀ is 38.93μm can be prepared. In addition, oxalic acid concentration 0.8mol/L, oxalic acid addition rate 3mL/min, gadolinium chloride concentration 0.75mol/L, the