This paper describes the preparation of Fe16N2 nanoparticles by reduction of iron nitrate. First, α-Fe nanoparticles were prepared by reduction of iron nitrate powder under hydrogen flow at 623 K for 5 h. The α-Fe nanoparticles with the size of about 140 nm in SEM image, were then nitrided under an ammonia flow at 423 K for 72 h. The sample consisted of Fe16N2 and α-Fe phases from XRD analyses and showed the magnetization of 207 A m2 kg-1 under magnetic field of 1.43 MA m-1 at room temperature. The average particle size was revealed as 140 nm by TEM observations. To investigate the possibility of the obtained nanoparticles as microwave absorption materials, the electromagnetic wave absorption properties were investigated in a composite of the obtained nanoparticles and resin. The sample showed a good microwave absorption properties (Reflection loss: R.L.<-20 dB) in 15~19 GHz range. Therefore, it is concluded that Fe16N2 nanoparticles have a possibility to become a candidate for microwave absorbers in 10~GHz range.