A method for preparing a solid of ruthenium nitrosyl nitrate using a ruthenium-containing spent catalyst, the method comprising the following steps: 1) drying a ruthenium-containing spent catalyst, and calcining the spent catalyst at a temperature of between 300 and 500°C for between 2 and 4 hours, and cooling to room temperature, whereby yielding a black ruthenium-containing solid; 2) grinding the black ruthenium-containing solid obtained in step 1) to yield a powder, introducing the powder to a fluidized bed reactor, aerating the fluidized bed reactor with nitrogen or an inert gas for between 0.5 and 2 hours, charging hydrogen, heating the fluidized bed reactor to a temperature of between 100 and 600°C for a reduction reaction, whereby yielding a metal of ruthenium; 3) contacting a mixed gas of ozone and air with the metal of ruthenium obtained in step 2), allowing the mixed gas and the metal of ruthenium to react at a temperature of between 600 and 650°C, whereby yielding a gas of ruthenium tetroxide; 4) introducing the gas of ruthenium tetroxide obtained in step 3) into a three-stage absorption plant comprising a nitric acid solution, whereby yielding an acid solution comprising ruthenium nitrate; 5) adding a solid of sodium nitrite to the acid solution comprising ruthenium nitrate obtained in step 4), stirring, and heating a resulting solution in the state of micro-boiling reflux, whereby yielding a solution of ruthenium nitrosyl nitrate; and 6) extracting the solution of ruthenium nitrosyl nitrate obtained in step 5) with anhydrous ether, collecting and evaporating an extraction solution for removal of ether, whereby yielding a solid of ruthenium nitrosyl nitrate. 1) drying a ruthenium-containing spent catalyst, and calcining the spent catalyst at a temperature of between 300 and 500°C for between 2 and 4 hours, and cooling to room temperature, whereby yielding a black ruthenium-containing solid; 2) grinding the black ruthenium-containing solid obtained in step 1) to yield a powder, introducing the powder to a fluidized bed reactor, aerating the fluidized bed reactor with nitrogen or an inert gas for between 0.5 and 2 hours, charging hydrogen, heating the fluidized bed reactor to a temperature of between 100 and 600°C for a reduction reaction, whereby yielding a metal of ruthenium; 3) contacting a mixed gas of ozone and air with the metal of ruthenium obtained in step 2), allowing the mixed gas and the metal of ruthenium to react at a temperature of between 600 and 650°C, whereby yielding a gas of ruthenium tetroxide; 4) introducing the gas of ruthenium tetroxide obtained in step 3) into a three-stage absorption plant comprising a nitric acid solution, whereby yielding an acid solution comprising ruthenium nitrate; 5) adding a solid of sodium nitrite to the acid solution comprising ruthenium nitrate obtained in step 4), stirring, and heating a resulting solution in the state of micro-boiling reflux, whereby yielding a solution of ruthenium nitrosyl nitrate; and 6) extracting the solution of ruthenium nitrosyl nitrate obtained in step 5) with anhydrous ether, collecting and evaporating an extraction solution for removal of ether, whereby yielding a solid of ruthenium nitrosyl nitrate.