A method for the simultaneous determination of acetonitrile and acrylonitrile in ambient air by using gas chromatography was established. Ambient air samples collected by activated carbon and carbon disulfide were desorbed into gas chromatograph, separated by capillary column and detected by hydrogen flame ionization detector. This method had good separation effect for the two components. It was simple, fast, linear, sensitive, accurate and reliable. It was suitable for monitoring acetonitrile and acrylonitrile in ambient air.