Abstract: After sample dissolution with mixed acid of HF-HNO3-HCl-HClO4, 50 g/L sodium carbonate solution was used for separation of coexistent elements with separation time of 30 min. Fe, Zn, Ca, Co, Ni, Cu and Mn remained in the residue without any interference on determination of trace uranium by ultraviolet fluorescence spectrometry. The detection limit of the method for uranium is 0.009 μg/g and precision is 3.37%～7.06%RSD (n=12). The method has been applied to the determination of trace uranium in geochemical samples with satisfactory results and is applicable to the determination of trace uranium in soil, stream sediment and rock samples with higher contents of Fe, Zn, Ca, Co, Ni, Cu and Mn.