Invisible set-off compounds from print in reverse side of food packaging was detected and identified using ambient ionization-accurate mass spectrometry (AMI-AMS). The result showed that AMI-AMS is able to detect print set-off and identify different compounds without any pretreatment of sample; the structure of the compounds detected can be confirmed using gas chromatographic-mass spectrometric (GC-MS) analysis; compared with GC-MS, AMI-AMS has the advantages of simple, fast, accurate, and convenient for high throughput analysis.