Abstract: The principle and technique of determination of ²³⁵U/²³⁸U isotope abundance ratio by fission yield ratio were discussed. Samples were irradiated by 14.8 MeV neutrons for short time, then γ rays spectra were measured with HPGe spectrometry system. From characteristic γ rays of separate fission products, the weighted average fission yields were got. Then correlative curves of ²³⁵U/²³⁸U isotope abundance ratio versus fission yield ratio for several product pairs were got.