Abstract: A method for determination of trace Zr in U 3O 8 by ICP MS after TTA/xylene extraction is reported. The sample is converted to UO 2(NO 3) 2 with HNO 3 and the Zr is separated from matrix element uranium by TTA/xylene in 4 mol/L HNO 3. Then Zr is back extracted by 8 mol/L HNO 3 after lowering the concentration 10 times of organic phase and is determined by ICP MS directly after lowering the concentration of aqueous phase 10 times again. The analytical results of uranium standard substance are talled with recommendatory value.