Abstract: From March 29, 2015 to May 6, seawater samples were collected from Qingdao to Northwest Pacific Ocean on Dongfanghong 2.Mercury species were determined using the method of in-situ and indoor to study their distribution characteristics.This research will be helpful to understand the concentration of mercury from Yellow Sea to Northwest Pacific Ocean and the migration of mercury in areas.The total mercury(THg) concentration from Yellow Sea to Northwest Pacific Ocean varied from 0.11 ng/L to 2.50 ng/L, with the average of 0.75±0.51 ng/L.THg concentration was high in marginal sea of China and low in ocean.The reactive mercury (RHg) concentration varied from 0.10 ng/L to 1.45 ng/L with the average of 0.33±0.24 ng/L, and the RHg/THg varied from 15.4% to 88.6% with the average of 48.4%.RHg concentration had a positive correlation with water temperature (r=0.494*, P=0.045).The concentration of dissolved gaseous mercury (DGM) varied from 11.7 pg/L to 105.7 pg/L with the average of 39.6 ±22.9 pg/L.DGM concentration had a positive correlation with temperature (r=0.633*, P=0.011) and negative correlation with wind speed (r=-0.660**, P=0.006).DGM concentration increased from Yellow Sea to Northwest Pacific Ocean.Affected by illumination intensity, the measurements showed a noticeable diurnal of DGM with high concentration during daytime and low concentration during nighttime.