On-line coupling continuous-flow liquid membrane extraction (CFLME) with HPLC, a novel automatic system was developed for the determination of sulfonylurea herbicides in water. After an automatic trace-enrichment process by CFLME, which is the combination of continuous flow liquid-liquid extraction and support liquid membrane (SLM) extraction, the target analytes were concentrated in 50 μl of 0.2 M Na 2 CO 3 -NaHCO 3 (pH 10.0) buffer. The concentrated sample solutions were injected directly onto a C 1 8 analytical column with a valve, and detected at 240 nm with a diode array detector. Metsulfuron methyl (MSM), and DPX-A 7881 were baseline separated with a mobile phase consisting of methanol and 67 mM KH 2 PO 4 -Na 2 HPO 4 (pH 5.91) buffer (45+55, v+v) at a flow-rate of 1.0 ml min - 1 . With an enrichment time of 10 min and enrichment sample volume of 20 ml, the enrichment factors and detection limits are 100 and 0.05 μg l - 1 for MSM, and 96 and 0.1 μg l - 1 for DPX-A 7881, respectively. The linear range and precision (RSD) are 0.1-50 μg l - 1 and 7.0% for MSM, and 0.2-50 μg l - 1 and 9.2% for DPX-A 7881, respectively. This proposed method was applied to determine MSM and DPX-A 7881 in seawater, tap water, and bottled mineral water with spiked recoveries in the range of 83-95% for MSM and 88-100% for DPX-A 7881, respectively.