The invention discloses an ammonium dinitramide and crown ether eutectic oxidant and a preparation method thereof. The preparation method comprises the following steps: (1) adding ammonium dinitramide into a crystallization solvent, heating the temperature of the solvent to 20 DEG C to 50 DEG C, and carrying out dissolving and filtrating, so as to obtain an ammonium dinitramide saturated solution; adding a crown ether into the ammonium dinitramide saturated solution, and carrying out dissolving and filtrating, so as to obtain an ammonium dinitramide and crown ether cocrystallization saturated solution; (2) filtrating the ammonium dinitramide and crown ether mixed saturated solution, placing the filtrate in culture dishes separately, then, carrying out standing in a constant-temperature incubator to evaporate the solvent and lower the degree of supersaturation of the solution, and carrying out crystal nucleus forming, crystal growing, filtrating and drying sequentially, thereby obtaining the ammonium dinitramide/crown ether eutectic oxidant. The ammonium dinitramide/crown ether eutectic oxidant prepared by the method has relatively low hygroscopicity and meanwhile has an excellent free-running property, thereby having a relatively good application prospect in low-sensitivity propellants as a composition ingredient of propellants and pyrotechnic compositions.