A sample pretreatment method for the determination of 18 chlorophenols (CPs) in aqueous samples by derivatization liquid-phase microextraction (LPME) was investigated using gas chromatography-mass spectrometry. Derivatization reagent was spiked into the extraction solvent to combine derivatization and extraction into one step. High sensitivity of 18 CPs derivatives could be achieved after optimization of several parameters such as extraction solvent, percentage of derivatization reagent, extraction time, pH, and ionic strength. The results from the optimal method showed that calibration ranging from 0.5 to 500microgL(-1) could be achieved with the RSDs between 1.75% and 9.39%, and the limits of detection (LOD) are ranging from 0.01 to 0.12microgL(-1) for the CPs. Moreover, the proposed LPME method was compared with solid-phase microextraction (SPME) coupled with on-fiber derivatization technique. The results suggested that using both methods are quite agreeable. Furthermore, the recoveries of LPME evaluated by spiked environmental samples ranged from 87.9% (3,5-DCP) to 114.7% (2,3,5,6-TeCP), and environmental water samples collected from the Pearl River were analyzed with the optimized LPME method, the concentrations of 18 CPs ranged from 0.0237microgL(-1) (3,5-DCP) to 0.3623microgL(-1) (2,3,6-TCP).