Flusulfamide, a sulfonanilide family fungicide, is used to control clubroot caused by Plamodiophora brassicae Woronin in Chinese cabbage in Taiwan. To know the amounts of residues on the crops are very important in our IES (Inspection and Education System); unfortunately, information on analytical methods to determine flusulfamide residues is very rare. An analytical method was developed to detect the flusulfamide residues in Chinese kale and Chinese cabbage. The residue of sulfonanilide in vegetable samples were extracted by acetone and partitioned to dichloromethane and cleaned up by SPE (solid phase extraction). The residue was further methylated with methyl iodide. The derivatives were measured by GC-ECD and identified by GC/MS. The recovery of flusulfamide in Chinese kale and Chinese cabbage were 92.6 and 93.2% by fortification with 0.005 to 0.5 μg/g, respectively. The detection limits were 0.001 μg/g for crops. The method was applied to the determination of flusulfamide residues in crops from treated field.