Abstract: Mercury methylation by microbes plays a key role in mercury biogeochemical cycle, and closely related with public health. It has received increasing attention. The paper reviewed the research history and development state, the factors affecting mercury methylation rates, the methylation mechanism and the main study methods used in this research field. It is pointed out that determining the specific microbes in specific ecosystem, making out the mechanism of microbial methylation, demethylation and species-specific stable isotope fractionation of mercury during microbial methylation will become the hot and focal topics of researches.

Key words: Rhizobium, Mixed cropping, Wheat, Astragalus, Biomass, Nitrogen