Stream sediments constitute one of the main surface media. The compositions of organic carbon, fulvic acid, humic acid and humin in stream sediments were analyzed, and the distribution characteristics of Cu, Pb, Zn, Ag, Sb, Mn, Mo, Ni, As and Hg in fulvic acid and humic acid were investigated. The results show that humin occupies two thirds of the organic matter, which is the dominant part of the organic matter, whereas fulvic acid and humic acids occupy one third of the organic matter, which exert strong geochemical effects. Geochemical activities of most elements in stream sediments are affected by fulvic acid, but Hg, Ag, Pb and Sb are affected by humic acid.