Abstract: SPE-HPLC was applied to the determinations of 3 sulfonamides in water, i.e., sulfamethoxazole, sulfisoxazole and sulfamonomethoxine. The sulfonamides in sample were enriched on the self-made cation-exchange SPE column, and separated on C18 column. A mixed solution of acetonitrile and 2% (φ) acetic acid solution (mixed in the a ratio of 1 to 5) was used as mobile phase. UV-detection at 270 nm was adopted in the determination. Linear relationships between values of peak area and mass concentration of the 3 sulfonamides were kept in the same range of 0.005-0.5 mg·L-1, with detection limits (3S/N) in the range of 2.4-3.7 μg·L-1. The proposed method was applied to the determination of the 3 sulfonamides in water sample, giving results of recovery obtained by standard addition method in the range from 88.6% to 103% and RSD′s (n=6) in the range of 2.6% to 4.4%.