Abstract: The nylon 12 sample (0.100 g) was dissolved for 3 h with 1.0 mL of hexafluoroisopropanol at 45℃. After cooling, 0.10 mL of the above solution was taken and 2.0 g of ethyl acetate was added. After shaking up in airtight container, the mixed solution was stood for 2 h. The supernatant liquid was filtered on 0.45 μm needle filter of hydrophilic PTFE. GC was applied to the determination of 4 monomers in the filtrate. The 4 monomers were separated on RXI-17 chromatographic column (30 m×0.25 mm, 0.25 μm) and detected by FID. Linear relationships between values of peak area and mass concentration of the 4 monomers were kept in the same range of 2.0-200.0 mg·L^-1, with detection limits (3S/N) in the range of 0.7-2.0 mg·L^-1. The proposed method was applied to the analysis of the nylon 12 sample, giving values of recovery found by standard addition method and RSDs (n=6) of determined values in the ranges of 93.7%-115% and 1.5%-3.2% respectively.