Abstract: The vegetable oil sample (2.500 g) was extracted with 10 mL of methanol (7+3) solution and then centrifugated for 10 min at the speed of 6 000 r·min^-1. After freezing for 30 min at -20℃, the supernatant was filtered with 0.22 μm organic filter membrane. UHPLC-MS/MS was applied to the rapid determination of aflatoxin B₁ in the filtrate. Accucore aQ chromatographic column was used as stationary phase, and the mixture of 0.1% (φ) formic acid solution (containing 5 mmol·L^-1 ammonium acetate) and methanol mixed in different ratios was used as mobile phase in gradient elution. ESI⁺ and the selected ion monitoring mode were adopted in MS/MS. Linear relationship between values of peak area and mass concentration of aflatoxin B₁ was kept in the range of 0.50-10.00 μg·L^-1, with detection limit (3S/N) of 0.02 μg·kg^-1. On the base of blank sample, test for recovery was made by standard addition method; values of recovery found were in the range of 86.0%-96.6%, with RSDs (n=6) of recovery amounts in the range of 5.6%-8.4%.