Objective This thesis aims at establishing the measure method of aflatoxin in cereals with supercritical fluid extraction-supercritical fluid chromatography-mass spectrometer/mass spectrometer (SFE-SFC-MS/MS) method. Methods Samples were extracted by supercritical CO₂-methanol(98∶2,V/V). The analysis was carried out on an Shim-pack UC-X RP C₁₈ column (150 mm×4.6 mm, 3 μm) with isocratic elution using a mobile phase of supercritical CO₂ and methanol. Mass spectrometry acquisition was done in the positive ion mode and the analytes were detected in the multiple reaction monitoring (MRM) mode. Results The correlation coefficients of aflatoxin B₁, B₂, G₁ and G₂ were above 0.998 in the range of 0.5-20 ng. The method had good linear relation. The recovery rate in samples of rice and corn grit were 92.3%-107.9%,93.0%-106.1%,93.4%-104.9%,92.8%-102.2% respectively, relative standard deviations of 3.0%-4.3%, 3.2%-4.5%, 3.0%-4.6%, 3.0%-4.5%(n=6) respectively. The limit of quantitation was 0.1 μg/kg. Conclusion This method was quick, simple, safe and accurate. It was available for measuring the amount of aflatoxin B₁, B₂, G₁, G₂ in cereals.