A method for simultaneous determination of eight isocyanates in medicinal composite packaging bags was established by gas chromatography-mass spectrometry (GC-MS). The composite packaging bag was cut into small pieces no larger than 5 mm×5 mm, and then extracted by dichloromethane for 40 min. The extraction solution was analyzed by GC-MS after concentration by nitrogen blowing. Eight isocyanates could be separated and detected using TG-5MS column with injection temperature of 200 ℃ and initial temperature of column incubator of 40 ℃. Eight isocyanates had a good linear relationships in the range of 0.02 to 5.0 mg/L with the correlation coefficient greater than 0.997. The detection limit was in the range of 0.001~0.006 mg/kg. The recovery for accuracy at low, medium and high concentration levels was ranged from 80.3% to 111.7%, and the relative standard deviation for repeatability was between 0.6% and 5.1%. This method is simple, sensitive and accurate, which can provide technical support for the detection and analysis of isocyanate in medicinal composite packaging bag.