In view of the wide application of organosilicon bifunctional structure in industry, the most effective disproportionation solution is used by the new catalyst to prepare the largest and the most versatile organic silicon monomer dimethyldichlorosilane. However, there are still remaining doubts on the disproportionation mechanism of the catalyst. The Density Functional Theory (DFT) was used to theoretically calculate the disproportionation mechanism of 5 T clusters ZSM‐5@γ‐Al2O3 series catalysts at the B3LYP/6–311++G(3df, 2pd) level. The properties were verified and the catalytic effects of different active sites pre‐ and post‐ modified by AlCl3 were calculated and compared. The active center of HZSM‐5@γ‐Al2O3 was proton, and that of AlCl3/ZSM‐5@γ‐Al2O3 changed to lewis acidic center. The presence of the lewis acid center enhances the total activity of the catalyst to some extent. The catalytic activity of the 5 T cluster ZSM‐5@γ‐Al2O3 catalyst modified by AlCl3 was higher, which was the same as the experimental results.