The innovative idea and excellent performance of the SKI series catalysts for isomerization of C₈ aromatics are elaborated. With the zeolite solid acid instead of halogen, not only the complicated chlorine supplement and the alkaline washing in the operation are eliminated but also the equipment corrosion is prevented and the operation environment is improved. As a result, the catalyst is environmental - friendly. The thermodynamic equilibrium can be approached for the isomerization of the mixed C₈ aromatics with poor para - xylene by the SKI Series catalysts. The selectivity for the C₈ aromatics is more than 97% and the catalyst life-span is more than 5 years. The achievement of the realistic productivity derived from the scientific and technological research was made through the substitution of the imported catalysts with the SKI series catalyst in the 7 imported commercial units