Inorganic nitrogen (N) immobilization in soils could enhance the capacity of soil N retention and thus reduce the potential risk of NO₃^-1 leaching, NH₃ volatilization as well as N₂O and NO emissions losses. Biotic and abiotic inorganic N immobilization as well as their significance in soil N cycling is introduced in this paper. The paper discusses preliminarily the mechanisms and influence factors of both biotic and abiotic inorganic N immobilization and puts forward orientation of the future research. In particular, neither the mechanism nor the kinetics of abiotic immobilization of NO₃^-1-N are known. So far, only the ferrous wheel hypothesis could explain abiotic immobilization of NO₃^-1-N in forest soils. However, the ferrous wheel hypothesis has not been fully demonstrated and therefore further studies about abiotic immobilization of NO₃^-1-N are extremely needed.