Denitrification is one of important soil microbial processes leading to the production of nitrous oxide(N2O).The N2O producing and reducing activities appeared to differ in their heavy metal tolerance,which may affect the N2O emission in heavy metal polluted soils.In this study,the polluted and non-polluted soils were collected respectively from four rice paddy fields,which had been polluted with heavy metals for more than three decades.Heavy metal pollution markedly affected composition of both nirK and nosZ denitrifiers.