In this study, a method of dispersive liquid phase microextraction combined with the flame atomic absorption spectrometry was proposed for the determination of trace Hg using diphenylthiocarbazone as chelating reagent. Several factors which have effect on the microextraction efficiency of Hg, such as pH, extraction and dispersive solvent type and their volume, concentration of the chelating agent, extraction time were investigated, and the optimized experimental conditions were established. After extraction, the enrichment factor was 68. The detection limit of the method was 45 ng mL-1, and the relative standard deviation for eight determinations of 2 µg mL-1 Hg was 1.7 %. The results for the determination of Hg in environmental water samples (tap water, well water, mineral water and Caspian sea water) have demonstrated the accuracy, recovery and applicability of the proposed method.