The first-principle technique has been employed to determine the atomic structure of nitrous oxide (N 2 O) monolayer and the N 2 O/Ag system in different coverage. The potential structures of N 2 O monolayer on the virtual and real Ag(100), Ag(110) and Ag(111) surfaces have been proposed. The stable structure is N 2 O monolayer adsorbed on Ag(110) through the terminal N atom in the top site with the coverage is 0.50 ML, which is not agree with experimental work done with NEXAFS of N 2 O on Ag(110). The structural parameters are as follow: the adsorption height is 2.37 Å, the angle between the N–N bond of the molecule and the substrate is 37°, the bond angle of absorbed N 2 O is 177°. The interaction between the monolayer and the Ag surface is weak, and the chemisorption energy and the adsorption height confirm the conclusion.