Abstract: The radioactive impurities in La2O3 must be determined in order to remove them.α-spectroscopy and γ-spectroscopy analysis of the lanthanum oxide samples have been carried out. The results of the experiments indicate that there are all long-live nucilides of the three natural radioactive series in La2O3. The most important nuclides are the daughters of 227Ac. The content of 227Ac in La2O3 is measured by γ-spectroscopy analysis and extraction-liquid scintillation counting. The results obtained from these two methods are concordant.