A simple and efficient approach for the preparation of hydroxylammonium nitrate from the hydrolysis reaction of cyclohexanone oxime in the presence of nitric acid has been developed in this work. The effects of the molar ratio of cyclohexanone oxime to nitric acid, the amount of water, the reaction temperature, the reaction time, and the extraction solvent on the hydrolysis reaction were investigated. The results indicated that the conversion of cyclohexanone oxime can reach 62.6% with 96.9% selectivity to hydroxylammonium nitrate and 97.4% selectivity to cyclohexanone under the optimal reaction conditions. In addition, the possible acid-catalyzed hydrolysis reaction mechanism is discussed. This work might be very significant for establishing such a preparation method for hydroxylammonium salts from the hydrolysis reaction of oxime in the chemistry and chemical engineering fields.