The invention relates to a preparation method of a C8 aromatic isomerization catalyst. The preparation method includes the following steps that 1, a hydrogen type ZSM-5 molecular sieve is treated through an organic acid solution, dried and roasted, and an organic acid modified ZSM-5 molecular sieve is obtained and marked as Z-1; 2, the Z-1 molecular sieve in the step 1 is soaked in a silicone-containing compound solution, dried and roasted, and a Z-1 molecular sieve with the surface covered with silicon dioxide is obtained and marked as Z-2; 3, the Z-2 molecular sieve in the step 2 and inorganic binder are mixed, kneaded, extruded and formed, dried and roasted, and a carrier is obtained; 4, the carrier in the step 3 is soaked in an VIII group metal precursor solution, dried and roasted, and the C8 aromatic isomerization catalyst is obtained. The catalyst is used for a C8 aromatic isomerization reaction, the selectivity of benzene is good, the yield of xylene is high, the reaction air speed is high, the stability of the catalyst is good, and the concentration of paraxylene in a product reaches and even exceeds the thermodynamic equilibrium value.