We discussed the climatic and environmental changes from the mid -18 th century to the early 21st century in Heihe River downstream by dating the profile of Tamarix Ramosissima nebkha with AMS14C and analyzing the grain size and Hg concentration of its sediments.Fine sand is prevalent in nebkha sediments.And the unimodality of the distribution frequency curves suggest that the formation and development of nebkha is dominated by aeolian sedimentation.The content of coarse grains,which indicates the winter monsoon intensity,records the transition from Little Ice Age to modern global warming and two cold periods in the past 100 years:1910s-1920s and 1950s-1960s.Then,mercury in nebkha sediments comes mainly from humanity's industrial actions.The range of Hg concentration of the profile has three peaks which respectively correspond with the silver mining Spanish America in late 18th century,the Gold Rush in mid-to-late 19th century,World War II and the post-war economic resurrection.Besides,Hg concentration are abnormal high in two samples,and it's connected with the increase of mercury deposition flux which caused by the volcanic eruption in1815 and 1883.