Nano Fe4N powder has been successfully prepared by the combination between high pressure combined method of reduction and nitriding and molecular dynamics (MD) simulation. The phase, composition, morphology, and magnetic properties have been preliminarily characterized by XRD, TEM, and VSM to investigate the influence of temperature, time, ammonia hydrogen ratio, and pressure during reaction process on the preparation. The results indicate that the preferable nano Fe4N powder of the average size around 35[Formula: see text]nm could be obtained nitriding at 0.4[Formula: see text]MPa and 673[Formula: see text]K for 2.5[Formula: see text]hours with the ammonia hydrogen ratio being 3:1. The results of magnetic detection show that the nano Fe4N produced here is a fairly desirable soft magnetic material with Ms[Formula: see text][Formula: see text][Formula: see text]169.70[Formula: see text]emu/g. This process could reduce the reaction temperature and shorten the reaction time, which is of important significance to the industrial production of nano Fe4N powder.