Abstract: Studies on the determination of trichlorobenzenes (TCBs) in sea water, by dispersive liquid-liquid microextraction (DLLME)-gas chromatography/mass (GC/MS) method, have been carried out. Parameters, such as the kind and volume of extraction solvent, disperser solvent, extraction time and temperature, were intensively studied and optimized. The result showed that the optimized DLLME condition was obtained when 0.5 mL of actone (disperser solvent), containing 10 L chlorobenze (extraction solvent) was used for the treatment of 10 mL synthetic seawater samples with 10 min-ultrasonic extaction at 25℃. Overall recoveries of the present method were 97.8%~102.5%with RSD values at 2.8%~6.6%. The detective limits for 1, 3, 5-, 1, 2, 4- and 1, 2, 3- TCB were 1.5 g/L, 0.5 g/L and 2.0 g/L, respectively. Comparing with traditional sample preparation procedures, e. g. head-space, liquid-liquid extraction and solid phase extraction, the present method was accurate, better enrichment property, better repeatability, easier to be operated with less interference. The present method has been applied for the determination of the TCBs residue concentration of 5 real samples. The result showed that two of them were found to contain 2~3 kinds of these TCBs. The TCBs detected in the studied samples were at concentration of(1.9~6.7)g/L.