The responses of delta N-15-N2O isotopic signatures to nitrogen (N) fertilization in in situ soils are not yet clear in agricultural field settings. We therefore conducted a 1-year field experiment to assess how N fertilization (0 and 400 kg N ha(-1) year(-1), N0 and N400) affects the delta N-15-N2O isotopic signatures both at soil surface and in soil profile (0-3 m) in a wheat-maize rotation in North China. N fertilization increased N2O concentrations by 18-79% in the soil profile. It increased N2O fluxes by 9 times and 1-7 times at the soil surface and 0-0.9 m soil depth, respectively. In comparison, N fertilization reduced delta N-15-N2O values by 10-74% in the soil profile. It reduced delta N-15-N2O isotopic signatures at the soil surface and in the soil profile by 18% and 33%, respectively. The delta N-15-N2O isotopic signature was dominated by substrate delta N-15 signature and N isotope fractionation during cold and warm seasons, respectively. Our results indicate that denitrification steps of NO3- -> N2O dominated N2O production (over 99%) in the N0 treatment and the N400 treatment during N-fertilizer-free period. Following N fertilization, the NO3- -> N2O dominated N2O production (over 99%) in the soil profile, N2O flux from the soil surface was mostly derived from NO3- -> N2O and less from NH4+ -> N2O. Overall, denitrification was found to dominate soil N2O transformation metabolism in the wheat-maize rotation cropland in North China.