During the 5th China Arctic Research Expedition of the R/V Xuelong (June–September, 2012) total gaseous mercury (TGM) in the marine boundary layer along the route was measured. The spatial distribution of TGM was determined from Shanghai to the Bering Strait along the Northwestern-Pacific volcanic belt and around Iceland outside the Arctic Ocean. TGM ranged from 0.17 to 9.03 ng/m³ with a mean of 1.86 ± 1.21 ng/m³ (median: 1.55 ng/m³). Several peaks along the cruise exceeded 4.0 ng/m³. TGM means in leg1 and leg4 (near Japan) were 1.99 ± 0.71 ng/m³ and 2.56 ± 1.39 ng/m³, respectively. In leg2 and leg3 near the Kamchatka peninsula, TGM was 1.23 ± 0.55 ng/m³ and 2.78 ± 1.42 ng/m³, respectively. In leg5 near Iceland TGM was 1.39 ± 1.02 ng/m³ with relatively high value in Reykjavik harbor (mean: 1.91 ± 1.27 ng/m³). Based upon backward air trajectory, trace gas CO, meteorological/hydrologic data, and volcanic degassing information, relatively greater TGM values were associated with the role of ocean emissions, volcanic, and other geothermal activities.