During DY105-17 cruise onboard the R/V “Da Yang Yi Hao” in 2005,methane concentrations in the wa-ter column above Logachev hydrothermal vent field were measured by applying stripping/trapping-gas chromatographic (GC) and the distinct methane plumes were detected. Results show that the back-ground methane concentration within the Logachev area is from 1.05 nmol/L to 1.68 nmol/L,signifi-cantly higher than the background level of the Atlantic abyssal plain of 0.4―0.5 nmol/L,suggesting that hydrothermal venting is a major source of dissolved methane to the ocean. The highest anomalies of methane concentrations in the water column range from 7.14 nmol/L to 113.9 nmol/L and occur just at 180―500 m above the seafloor. The distribution of methane concentration and the structural charac-teristics of hydrothermal plumes are strongly influenced by the supply of underlying hydrothermal fluids,the mixing process of ocean bottom currents and the microbial oxidation. Furthermore,the dif-ferences in distribution of methane plume between the station MAR-CTD3 and the other stations indi-cate a probable unknown hydrothermal vent site nearby. There occurs high concentration of methane along with temperature and nephelometry anomalies,which strongly confirms that the subtle meas-urement of methane concentration in water column is one of the effective ways to locate active sites of hydrothermal venting. During DY105-17 cruise onboard the R / V “Da Yang Yi Hao” in 2005, methane concentrations in the wa-ter column above Logachev hydrothermal vent field were measured by applying stripping / trapping-gas chromatographic (GC) and the distinct methane plumes were detected. Results show that the back-ground methane concentration within the Logachev area is from 1.05 nmol / L to 1.68 nmol / L, signifi-cantly higher than the background level of the Atlantic abyssal plain of 0.4-0.5 nmol / L , suggesting that hydrothermal venting is a major source of dissolved methane to the ocean. The highest anomalies of methane concentrations in the water column range from 7.14 nmol / L to 113.9 nmol / L and occur just at 180-500 m above the seafloor. The distribution of methane concentration and the structural charac-teristics of hydrothermal plumes are strongly influenced by the supply of underlying hydrothermal fluids, the mixing process of ocean bottom currents and the microbial oxidation. Furthermore, the dif-ference s in distribution of methane plume between the station MAR-CTD3 and the other stations indi-cate a probable unknown hydrothermal vent site nearby. There occurs high concentration of methane along with temperature and nephelometry anomalies, which strongly confirms that the subtle meas-urement of methane concentration in water column is one of the effective ways to locate active sites of hydrothermal venting.