Denitrification is a microbial process in which oxidized nitrogen compounds are used as alternative electron acceptors for energy production.Denitrification release biosphere fixed nitrogen back to atmosphere and enable the global nitrogen cycling.Denitrification can benefit people by remediation of nitrogen polluted water system and in the opposite can cause great loss by removal of nitrogen fertilizer from fields.For many years,people know very little about denitrifiers in natural environment because of the limitations of culture-dependent research methods.The progress of molecular biology and biotechnology in recent years promote the development of environmental microbiology.People can extract DNA directly from environment and study environmental microbes with molecular marks combined many new techniques.This article reviewed the molecular ecological techniques on theresearch of environmental denitifiers and new progress in related research areas.