Abstract: The sample was immersed for 30min by refluxing in food stimulantwater, 4% (φ) acetic acid, 50% (φ) ethanol or 95% (φ) ethanol, or the sample was immersed for 30 min at 60℃ in isooctane and then dried by N₂-blowing and dissolved in 50% ethanol. The above solution was filtered through the microporous membrane of 0.45 μm, and then separated by UPLC using BEH C₁₈ chromatographic column as stationary phase, and a mixture of acetonitrile and water in various ratios as mobile phase in gradient elution. The detection wavelength was 210 nm. Linear relationships between values of peak area and mass concentration of caprolactam and laurolactam were found in definite ranges, with detection limits (3S/N) in the range of 1.0-2.0 mg·L^-1. Test for recovery was made by standard addition method, giving results in the range of 93.4%-100%, with RSDs (n=6) ranged from 1.7% to 3.2%.