A micellar electrokinetic capillary chromatographic method was used for quantitative determination of benzene, toluene and xylene in the groundwater at different depth. A fused silica capillary of 57 cm×50 μm(50 cm to detector) was used. Running buffer was a 2 0 mmol/L aqueous tetraborate solution containing 50 mmol/L sodium dodecyl sulfate(pH 9 16) and 20% methanol as an organic modifier. The voltage used was 25 kV. Detection wavelength was 200 nm. Benzene, toluene and xylene were separated well within 20 min. The calibration curves were linear over 4 3～52 8 mg/L. The minimum detectable concentrations were 2 3, 1 3 and 0 8 mg/L for three compounds respectively. The determination results showed that at the same well benzene concentration increased linearly with the increase of the well depth.
