Abstract: HPLC and AFS in hyphenation were applied to the determination of inorganic and organic mercury in water.The water sample was passed through DDTC modified C18 SPE microcolumn.The column was eluted with 4×1 mL of a mixture containing 10% (φ) of acetonitrile at a flow-rate of 1-2 mL·min-1.The eluates were collected,mixed and filtered.Chromatographic separation was made with the filtrate obtained,by using venusil MP C18 column as stationary phase and a mixture containing CH3CN,145 mmol·L-1 NH4OAC solution and 20 mmol·L-1 L-cysteine solution (mixed in the volumic ratio of 5+45+50) as mobile phase.Contents of Hg in the 3 species were determined by AFS under the prescribed condition.Linear relationship between values of peak area and concentration of mercury were found in the range of 0.5-20 μg·L-1.Detection limits (3S/N) were 1.6 ng·L-1 (for Hg2+),0.5 ng·L-1 (for MeHg) and 1.2 ng·L-1 (for EtHg).Values of recovery found by standard addition method were in the range of 71.2% to 95.2%,and values of RSD′s (n=6) in the range of 4.9%-10%.