【Objective】 A variety of dissolved organic matter (DOM) and microorganisms affect mercury transformation under anaerobic conditions by mediating biogeochemical cycles. However, it is still unclear how specific organic matter would affect mercury transformation under this condition. 【Method】 Using batch experiments, the effect of DOM and the co-culture of microorganisms on mercury transformation were investigated. Under simulated the anaerobic environment, three kinds of DOM(cysteine and glutathione containing sulfhydryl and fulvic acid) and two kinds of bacteria (Shewanella putrefaciens CN32 and Geobacter sulfurreducens PCA) were selected to create a reduction environment and methylated mercury, respectively. Batch experiments were carried out to investigate the effect of DOM and the co-culture of microorganisms on mercury transformation. 【Result】 The results showed that the unit cell adsorption/uptake capacity of G. sulfurreducens PCA for Hg(Ⅱ) was 69.0% of that of S. putrefaciens CN32. Cysteine and glutathione did not alter the proportion of intracellular mercury in G. sulfurreducens PCA, but the proportion of intracellular mercury in S. putrefaciens CN32 was decreased. In the culture of G. sulfurreducens PCA, cysteine promoted mercury reduction and methylation, glutathione promoted mercury reduction, and fulvic acid inhibited mercury reduction and methylation. In the co-culture system of S. putrefaciens CN32 and G. sulfurreducens PCA, the mercury methylation ratio was as high as 18.7%±3.1% after the addition of cysteine complexed mercury, which was mainly attributed to the enhancement of Hg methylation of G. sulfurreducens PCA by microbial co-culture. 【Conclusion】 The results of this study elucidate the mechanism of DOM and co-culture of microorganisms on mercury species transformation in anaerobic condition, and provide a theoretical basis for the remediation of mercury pollution in flooded paddy field wetland.