The nosZ gene encoded N2OR was cloned and expressed heterologously.One denitrifying strain named as Marinobacter hydrocarbonoclasticus NY4 was used in the experiment.The existence of N2OR in strain NY4 was confirmed by analyzing gaseous products produced by denitrification.The full-length nosZ gene (1 896 bp) was obtained by PCR amplification with a pairs of specific primers,which only shared 46.9% similarity with the nosZ gene from G. thermodenitrificans. The heterologous expression of the nosZ gene in Escherichia coli was carried out.The nosZ gene from strain NY4 was further expressed in E. coli.The activity of N2OR was successfully detected.The enzyme activity was (0.20±0.01) U/mg.