A method for preparing solid ruthenium nitrosyl nitrate, including: 1) drying a ruthenium-containing spent catalyst, and calcining the spent catalyst, and cooling to room temperature, whereby yielding a ruthenium-containing solid; 2) grinding the ruthenium-containing solid to yield a powder, introducing the powder to a fluidized bed reactor, aerating the fluidized bed reactor with nitrogen or an inert gas, charging hydrogen, whereby yielding ruthenium metal; 3) contacting a mixed gas of ozone and air with the ruthenium metal, whereby yielding gaseous ruthenium tetroxide; 4) introducing the gaseous ruthenium tetroxide into a three-stage absorption plant, whereby yielding an acid solution including ruthenium nitrate; 5) adding a solid of sodium nitrite to the acid solution, stirring, and heating a resulting solution, whereby yielding a solution of ruthenium nitrosyl nitrate; and 6) extracting the solution of ruthenium nitrosyl nitrate with anhydrous ether.