Humic acids have significant influences on iron reduction in soil and aquatic environment. In this paper, humic acids, extracted from weathering coal of Datong in Shanxi Province, lignite of Gongxian in Henan Province and Dianchi Lake sediment in Kunming of Yunnan Province, were used to investigate their influences on dissimilatory amorphous Fe(III) reduction in aquatic incubation experiment by inoculating soil suspension. Results indicated that single addition of humic acid showed small influence on iron reduction, while addition of humic acid accompanied with glucose intensified significantly iron reduction process in the culture medium. The effect on dissimilatory iron reduction increased with the increase of humic acid concentration added in the culture. Humic acids extracted from the different material had different effects on dissimilatory iron reduction because of the differences in the structures and complexities of thoese material, and the humic acid extracted from the weathering coal showed the strongest effect on dissimilatory iron reduction, but no significant difference between humic acids from lignite and lake sediment.