The ambient concentrations of total gaseous mercury (TGM) in Chongming Island, Shanghai, were continuously observed using the Tekran 2537B mercury analyzer from 15th September to 17th December, 2009. The average concentration of TGM during our observation is (2.50 +/- 1.50) ng x m(-3), much higher than the background TGM of north hemisphere. The TGM concentration increased from September to December. During September to December, the concentration peaks appear during 08:00-10:00 am and the daytime TGM concentration approximately equaled that in the night. The TGM in Chongming significantly correlated with concentrations of CO, which indicates that TGM most likely comes from the coal combustion of power plants and industrial boilers. The back trajectory analysis demonstrates the atmospheric mercury in Chongming Island mainly comes from inland China, especially Jiangsu province and Shandong province which locate in the northwest of Chongming. The mercury concentrations are lower in September and October since the airflow is mainly from the eastern ocean. In November and December, the atmospheric mercury content is much higher because the northwest wind brings the pollutants from the western industrial areas.