To establish a gas chromatography-mass spectrometry (GC-MS) method for the determination of 16 photoinitiator residuce levels in medicinal composite membranes，including benzophenone (BP) and 4-methylbenzophenone (4-MBP).

The samples were extracted by ethylacetate，separated with TR-5MS column. The mass spectrum was analyzed with EI ionization，positive ion mode and selective reaction monitoring (SRM) mode and quantified with internal standard method.

The 16 kinds of photoinitiators had good linear relationships in the range of 0.05-2.0 μg·mL^-1，and the correlation coefficients (r) were more than 0.997. The limits of detection (LODs) were 0.03 μg·mL^-1. The average recoveries were (n=6) ranged from 81.3% to 94.0%，with RSDs of 2.1%-6.2%. The detection rate of 4-Isopropylthioxanthone (4-ITX) in the medicinal composite membranes was 30%，and the highest content was 0.02 μg·cm^-2.

The method is accurate with high sensitivity and simple pretreatment，which can be used for the detecting the kinds of photoinitiators in medicinal composite membranes.