A method for determination of 3-monochloro-1,2-propanediol in soy sauce by gas chromatography-tandem mass spectrometry(GC-MS/MS)was established. The sample was injected into GC-MS/MS after cleaned and extracted by methanol. The qualitative and quantitative analysis was achieved by EI source, polarity capillary column, and MRM method. The RSD of the method was less than 4% (n=6), and average recovery was more than 80%. The liner range was in 0.05-1μg/mL and the limit of detection (LOD) was 0.0012μg/mL.