A method for processing spent ion-exchange resins is provided by reducing the volume of the spent ion-exchange resins through a wet oxidation process and solidifying the residual wet oxidation slurry and the waste solution with high efficiency. The method comprises of using barium hydroxide as a neutralization agent to adjust pH of the reaction solution so as to drive away ammonia from the solution, and as a conversion agent to convert sulfuric acid and sulfate obtained in the reaction into barium sulfate. The process can solidify the wet oxidation residue slurry and waste solution with high efficiency.