α-Hydrazinium nitrate (HN)with high purity was synthesized by neutralizing hydrazine and hydrazine dinitrate,and its crystallogram were obtained by X-ray powder diffraction. Results show that the average crystal size of HN is 185.3 nm,and the cell unit is in good order in the crystal,and the density is 1.688 g·cm^-3. The crystal parameters of HN are as following: monoclinic,P 21/n,a=0.8015 nm，b=0.5725 nm，c=0.8156 nm，β=92.3，V =0.374 nm³，D_c=1.688 g·cm^－3,Z=4.