A new method was established for the simultaneous determination of atrazine and ametryn residues in sugarcane juice by gas chromatography-mass spectrometry under selected ion monitoring(GC-MS/SIM).The pretreatment and chromatographic conditions were optimized.Under the optimal conditions,good linearities were obtained for 2 herbicides in the range of 0.00-0.60 mg/L with detection limits of 0.001 mg/L for both atrazine and ametryn.The average recoveries of 2 herbicide residues at spiked level of 0.050-0.100 mg/L were in the range of 93%-106%,with RSDs(n=6) of 4.4%-10.7%.The method showed the advantages of simplicity,repeatability,and sensitivity,and could be applied in the determination of atrazine and ametryn residues in sugarcane juice.