Abstract: In order to improve the precision of plutonium isotope abundance analysis by γ-spectrometry, the article fits the relative efficiency scaling curves of ²³⁹Pu and ²⁴¹Pu energy peaks in the energy region of 120-460 keV by studying the principle of relative efficiency scaling in γ-spectrometry and improves it by polynomial interpolation in response to the shortcoming of insufficient fitting accuracy in the traditional method, and finally improves the fitting effect of the previous and previous methods by comparing with the actual spectra. Finally, we compare the fitting effects of the improved method with the actual energy spectrum and conclude that the analytical accuracy is higher after the improvement than before. The work of the article is of great significance for the analysis of plutonium isotope abundance by the relative efficiency scale technique.