Oxalydihydrazinium dinitrate was synthesized via substitution, neutralization reactions using diethyl oxalates and hydrazine hydrate as starting materials with a total yield of 97%. The structure of OHDN was characterized by IR, ¹H NMR, ¹³CNMR, ¹⁵N NMR and elemental analysis. The hydrolysis reaction of oxalydihydrazide was thoroughly studied in dilutenitric acid, and the hydrolyzate are conformed to be oxalic acid and hydrazinium nitrate, and the optimized reaction conditions of OHDN are found to be as follows: reaction temperature 40 ℃, reaction time 2 h. Moreover, the chemical stability of OHDN in water was investigated, showing poor stability at high temperature and good stability at room temperature.The single crystal of OHDN·2H₂O was obtained and its crystal belongs to orthorhombic system, space group is P2(1)/n, a＝0.4639(13) nm, b＝1.0992(3) nm, c＝1.0570(3) nm, V＝0.5301(2) nm³, Z＝2, D_c＝1.755 g·cm^-3, F(000)＝292, R₁=0.0855, wR₂=0.0895.