Forest soils are an important source of nitrous oxide (N₂O), however, field observations of N₂O emission have often exhibited large variabilities when compared with managed agricultural lands. In the last decade, the number of forest N₂O studies has increased more than tenfold, but only few of them have looked into the interannual flux variabilities from regional scale. Here, we have collected 30 long-term N₂O monitoring studies (≥ 2 years) based on global database, and extracted variabilities (VAR_Flux) as well as relative variabilities (VAR_%, in proportions) of annual N₂O fluxes. The relationship of mean annual precipitation (MAP), mean annual temperature (MAT), and nitrogen (N) deposition with flux variabilities was examined to explore the underlying mechanisms for N₂O emission on the long-term scale. Our results show that mean VAR_Flux is 0.43 kg N ha^-1 yr^-1 and VAR_% is 28.68%. Across climatic zones, the subtropical forests have the largest annual N₂O fluxes, as well as the largest fluctuations among annual budgets, while the tropics were the smallest. We found that the regulating factors for VAR_Flux and VAR_% are fundamentally different, i.e., MAT and N input determine the annual fluxes as well as VAR_Flux while MAP and other limiting soil parameters determine VAR_%. The relative contributions of different seasons to flux variabilities were also explored, indicating that N₂O fluxes of warm and cool seasons are more responsible for the fluctuations in annual fluxes of the (sub)tropical and temperate forests, respectively. Overall, despite the limitation in interpretations due to few long-term studies from literature, this work highlights that significant interannual variabilities are common phenomenon for N₂O emission from different climatic zones forest soils; by unraveling the divergent drivers for VAR_Flux and VAR_%, we have provided the possibility of improving N₂O simulation models for constraining the heterogeneity of N₂O emission processes from climatic zones forest soils.