Abstract: Denitrification is an important part of N-cycling in ecosystem, and is closely associated with nitrate accumulation in groundwater and greenhouse gas emission. Various bacteria, fungi and archaea involved in denitrification play important roles in controlling rate and N₂O︰N₂ ratio of denitrification. Populations of denitrifiers are structured by long-term environmental factors. They respond to temperature, moisture, pH, O₂ content, nutrient availability and vegetation in different ways. Environmental factors indirectly control denitrification rate and enzyme production through affecting denitrifiers. The molecular technology application facilitates the study on denitrifiers in natural environments, and shows new directions for further understanding of correlation between denitrifier population structure and their function. This paper summarized research achievers in denitrifier population, and advanced a framework for future studies about connections between denitrifier population structure and function.