Abstract: A rapid method for determination of fluoroacetamide(FAA) exact mass by flow injection-electrospray ionization-time of flight-mass spectrometry was set up. FAA in rice bait was extracted by water and the extract was centrifuged at 4 000r/min for 5min. 0.1mL supernatant was diluted to 0.5mL by water. Inject 2μL for TOF-MS determination of FAA exact mass using p-toluidine(positive ion 108.081 3u) as lock mass. The determined FAA exact mass was 78.035 5u±1mu. The only mass interference within 78.035 5u±10mu is C 2H 7NS(positive ion 78.037 7u) and the difference can be discriminated by (M+2) isotope peak. The area ratio(FAA/p-toluidine) vs concentration of FAA is linear within the range of 10~150mg/L, linear correlative coefficient are higher than 0.99. The method is simple, specific and rapid. There were no interferences in blank rice. The method can be used for quantitative determination of FAA>15mg/kg in rice bait. It would take about half an hour to finish the procedure from sample preparation to TOF-MS detection.