This study extracts UF - 2 ions from UF 4 sample material for the first time so as to improve the measurement accuracy and sensitivity for accelerator mass spectrometry (AMS) measurement of 236 U. Compared to the commonly used UO - /UO 2 (or U 3 O 8 ) combination, the UF - 2 /UF 4 approach brings a higher beam current of extracted U-containing ions and lower interference from U isotopes ( 235 U in particular). The UF 4 prepared with the procedures developed in this work can provide a higher ratio of F - /O - and therefore lower interference from O-containing 235 U and 238 U molecular ions, compared with that from the UF 4 made by conventional liquid-phase reaction. The AMS experiment was carried out on the AMS system at China Institute of Atomic Energy (CIAE), where only a simple surface barrier detector was used to record ions and a reference 236 U sample with a 236 U/ 238 U ratio of 10 -10 was analyzed. The result shows that the measurement sensitivity of the UF - 2 /UF 4 approach is lower than 10 -10 and that the reference 236 U sample result is in agreement with the reference value within the uncertainty limits, with the relative uncertainty only 4%. In comparison, the measurement sensitivity of the UO - /U 3 O 8 combination approach is 10 -9 , and it cannot give a concrete value for the same reference sample using the same AMS system. If the sophisticated 500-ps-resolution time-of-flight detection system is used in combination with the UF - 2 /UF 4 approach, a sensitivity of 10 -13 (or lower) is expected.