Atmospheric aerosol affects climate, ecology, visibility, and public health and has attracted widespread attention. The fraction of inorganic aerosols in the atmosphere is significant and constitute about one-third of fine aerosol mass. The sources and formation processes of inorganic nitrogen aerosols in the atmosphere are with great uncertainty and therefore their long-term field measurement is critical. This study conducted a year-round field measurement of TSP, PM2.5 and PM1.0 in five different sites (ZJK, CP, CY DX, and TJ) in the Beijing-Tianjin-Hebei region to determine the concentrations of water-soluble inorganic ions (WSIIs) and also the isotopic composition of inorganic nitrogen (δ15N-NH4+, δ15N-NO3-, and δ18O-NO3-) to explore the sources and formation processes. The seasonal variation of δ15N-NO3- and δ15N-NH4+ were reflective of the relative contributions of the main source and also the effects of meteorological conditions. The source apportionment identified fossil fuel combustion (38.2 ~ 50.6%), agricultural emissions (18 ~ 24.7%), biomass burning (16.3 ~ 22.7%), and road dust/soil (8.7 ~ 23.4%) as the main sources of inorganic aerosols in Beijing-Tianjin-Hebei region. The located sources and regional migration (or transboundary pollution) contribute to the level of inorganic aerosol pollution. In winter, the aerosol of this region was affected by the air mass coming from the northwest. While in spring and summer, the air mass was mainly from the South China. The low temperature and high relative humidity favored the formation of inorganic nitrogen aerosol, while solar radiation affected the formation processes of the inorganic aerosols by changing the oxidation pathway of NO3- and also accelerating the volatilization and dissociation of NH4NO3. This study highlighted the main source contributions of inorganic nitrogen aerosol by utilizing N and O isotopes composition. Also, this study attached great importance in understanding the effects of meteorological conditions on formation and the contribution of regional transport.