Since the industrial revolution, it has been assumed that fossil-fuel combustions dominate increasing nitrogen oxide (NO ) emissions. However, it remains uncertain to the actual contribution of the non-fossil fuel NO to total NO emissions. Natural N isotopes of NO in precipitation (δ N ) have been widely employed for tracing atmospheric NO sources. Here, we compiled global δ N observations to evaluate the relative importance of fossil and non-fossil fuel NO emissions. We found that regional differences in human activities directly influenced spatial-temporal patterns of δ N variations. Further, isotope mass-balance and bottom-up calculations suggest that the non-fossil fuel NO accounts for 55 ± 7% of total NO emissions, reaching up to 21.6 ± 16.6Mt yr in East Asia, 7.4 ± 5.5Mt yr in Europe, and 21.8 ± 18.5Mt yr in North America, respectively. These results reveal the importance of non-fossil fuel NO emissions and provide direct evidence for making strategies on mitigating atmospheric NO pollution.