Abstract: In order to study the precipitation kinetics of oxalate, the nucleation and crystal growth kinetics of cerium oxalate instead of plutonium oxalate were studied. The simple method was proposed to determine the dilution ratio in the experiments of nucleation kinetics. At the temperature of 25-50 ℃, the nucleation and crystal growth rate equations of cerium oxalate were studied respectively under the conditions of cerium nitrate concentration of 0.030-0.400 mol/L, oxalic acid concentration of 0.250-0.800 mol/L and excess oxalic acid concentration of 0.100 mol/L in mother liquor. The results show that the dilution ratio has a great influence on the measurement of nucleation rate during nucleation, and the optimal dilution ratio is obtained when the S_n value defined is 1.65. The nucleation process of cerium oxalate is divided into homogeneous nucleation and heterogeneous nucleation. The nucleation rate equation can be expressed as R_N=A_N0·exp［-E_a/RT］·exp［-B_N/(ln S)²］, where at A_N0=3.86×1030/(m³·s), E_a=67.4 kJ/mol, B_N=55.3 at homogeneous nucleation; at heterogeneous nucleation, A_N0=3.10×10²⁰/(m³·s), E_a=19.1 kJ/mol, B_N=11.5. The crystal growth rate equation can be expressed as G=k_g0·exp［-E_a/RT］·δ^g(t), where kg0=4.81×10⁵ m/s, E_a=80.3 kJ/mol, g=2.09. The crystal growth of cerium oxalate is dominated by the interface reaction process. The apparatus and method of measurements can be used to study the nucleation and crystal growth kinetics of other oxalates.