Abstract: A GC/MS method was developed for the determination of cyanuric acid residue in package materials. The detection was performed by mass spectrometry with electro-spray ion mode. The results show that the standard curves for the cyanuric acid is linear, and the correlation coefficient(R2) is more than 0.99 in the range of 0.05-1.0 mg kg^－1. The average recovery is 98.8 to 105.3, and the relative standard deviations are range of 4.58%-8.51%. The limit of detection is 0.01 mg kg^－1.