Abstract: A method for the determination of benzo (a) pyrene in animal and vegetable oils (lard, peanut oil, camellia seed oil, soybean oil and blending oil) by on-line purification with dual-column and ultra-high-speed liquid chromatography was established. Benzo (a) pyrene was extracted by n-hexane-isopropanol solution, filtered and injected into the sample, and purified on-line by the dual-column system. The first column was used as separation and enrichment column, Kromasil anti-C18 (4.6 mm×150 mm, 5 μm) column was used; the second column was responsible for further separation and separation of benzo (a) Pyrene was separated by Chrom Spher PI (80 mm×3.0 mm, 5 μm) column. The results showed that the content of benzo(a) pyrene in the sample had a good linear relationship with the peak area in the range of 1.0-20.0 ng/mL. The correlation coefficient R2 was 0.999 6, and the detection limit was 0.08 μg/kg. Under the standard addition levels of 1.00, 5.00 and 10.00 g/kg, the recovery rate was 82.0%-91.6%, and the relative standard deviation was 1.89%-4.29%. This method could be used for the rapid detection of samples contaminated by benzo (a) pyrene such as animal and vegetable oils.