Abstract: PuO₂ was mixed with soil samples collected at a desert region in northern China. The mixture was classified with wet classification method and an improved Tessier’s sequential extraction method was applied to study the species of Pu in the contaminated soil particles, in order to evaluate the mobility of Pu at this site under supposed conditions. It is found that major part (about 73%-96%) of Pu is bounded to organic materials and existed as residual forms. There was a obvious linear relationship between the percentage of Pu species and the amount of organic material or illite. Less than 0.8% of Pu exists in exchangible form. The results show that Pu is difficult to migrate in such area.