Abstract: A method for determination of thorium i.e 23 trace elements in UF₄ is established. In this work, UF₄ was dissolved by HNO₃ and φ=30% H₂O₂ with a volume ratio 1∶1, then evaporated to dry repeatedly for the removal of F^-. By using a 15 mm×105 mm CL-TBP column extraction chromatography, Al i.e 22 trace elements were separated with uranium in 3 mol/L HNO₃, the sixth to fifteenth mL eluent were collected for determination by ICP-AES. The recovery of these elements is between 97%-113%, and the relative standard deviation (s_r) is better than 5%(n=5) unless Al, Ca, Ba and Bi. In 6 mol/L HCl, the uranium was separated by TBP levextred resin chromatography, and the thorium was determined by ICP-MS. The recovery of Th is between 91%-94%, and the s_r is within 5% (n=5), and the detection limit of this separation method is 0.037 μg/g UF₄.