An HPLC-UV analytical method was developed to determine ethylenediaminetetraacetic acid (EDTA) in dairy wastewater and surface water. The optimizing separation was achieved by reversed–phase ion-pair liquid chromatography on a C18 column using methanol as mobile phase solvent, tetrabutylammonium bromide as the ion-pair reagent in pH 3.3 formate buffer solution at a flow rate of 0.9 mL min⁻¹ with a UV detector at 265 nm. No interference of Ca, Mg or NO₃⁻ was detected. Method performance was evaluated in terms of linearity, repeatability and reproducibility. The method detection limit was 5 µg L⁻¹. The contents of EDTA in dairy effluents were 72 ~ 261 µg L⁻¹ at a large dairy site. A change of EDTA concentration was observed downstream of the dairy effluent discharge, but this was well under the predicted no effect concentration for aquatic ecosystem