Abstract: Choosing paddy slurry as the specimen of experiment, through the experiment of adding variant Cr (VI), we determined the concentration of extractable Fe (II) and Cr (VI) under the condition of flooded incubation, also discussed the effect of Cr (VI) on iron microbial reduction and discussed competitive relationship between Fe (III) and Cr (VI). The result showed: Below a certain concentration of Cr (VI), Cr join the iron microbial reduction process in paddy slurry and the concentration of Cr (VI) in soil can decreased notable; Beyond this concentration, Cr do harm to the microbe of iron reduction, make the iron microbial reduction process not happen and Cr (VI) can not be reduced in soil.