Abstract: The determination of uranium isotope ratio in uranium particle plays an important role in the analysis of environmental sampling for nuclear safeguards. The accurate determination methods of minor isotope ratio in uranium particle are not perfect now. In this paper, a new analytical technique of minor uranium isotope ratios in uranium particle for direct measurement was established by small-sized accelerator mass spectrometry. By using CRM series of uranium isotope standard samples, the uranium particles with different abundances and sizes were measured and analyzed. The results show that the relative error between the measured values and the nominal values of ²³⁴U/²³⁵U and ²³⁴U/²³⁶U from CRM-U200, CRM-U970 are less than 10% and 20% respectively. This method can be used for the highly sensitive determination of micro-sized uranium particle and provides a new technical route for minor isotope ratio analysis of uranium particle.