Abstract: Residual amount of dimethyl fumarate in packaging film and packaging bag was determined by GC and MS in hyphenation.The sample was extracted with ethyl acetate,and the dimethyl fumarate in the extract was purified by passing through needle filter head.In the GC-MS analysis,HP-5MS capillary chromatographic column (30 m×0.25 mm,0.25 μm) was used for separation,and modes of electron bombardment ionization ion source (EI) and full scan monitoring were adopted for measurements.Linear relationship between values of peak area and mass concentration of dimethyl fumarate was kept in the range of 0.5-100.0 mg·L-1,and lower limit of determination (10S/N) found was 0.1 mg·kg-1.Test for recovery was made by standard addition method at 6 concentration levels of 5.0,10.0,20.0,30.0,40.0,50.0 mg·kg-1,and the results obtained were in the range of 95.0%-102.5%,with values of RSD′s (n=6) less than 6%.