Abstract: γ-ray spectrometry is used to measure fast neutron reactor fuel's uranium enrichment; this kind method is one of most important nondestructive assay method. 235U enrichment in fast neutron reactor fuel is 64.4%. Measuring time is proportional to 235U enrichment in material. We measured several fuel rods. It is difficult to do accuracy measurement in high background condition. We choose professional hardware and software to do work. As a result, most deviation between measured 235U enrichment and true value less than±3%.