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Dimethyldichlorosilane is a basic raw material for preparing a variety of organosilicon materials.The disproportionation method to synthesize it can solve the problem brought by direct synthesis.The B3LYP/6-31G and MP2/6-311++ G(3df,2pd) methods were used to calculate the mechanism of the reaction catalyzed by localized core(4T)-shell catalyst.The energy barriers of the rate-determining steps of the main reaction at different active sites 1(5)～4 in the HZSM-5(4T)@γ-Al2O3 catalyst were 165.88,129.99,118.66 and 145.55 kJ·mol-1,respectively,and those in the side reaction are 131.98,146.28,146.53 and 164.17 kJ·mol-1,separately.The active site No.3 was the easiest one to participate in the catalytic reaction.The energy barriers of the rate-determining steps of the main reaction catalyzed by the AlCl3/HZSM-5(4T)@γ-Al2O3 catalyst,involving configurations a and b,are 105.12 and 110.39 kJ·mol-1,respectively,and those of the side reaction are 144.26 and 159.55 kJ·mol11,respectively.Both configurations produced dimethyldichlorosilane mainly,and configuration a is easier to catalyze the reaction process.And according to the bond order and locality analysis,the catalytic activity order was:configuration a ＞ configuration b.This conclusion matched with the reaction energy barrier analysis.The AlCl3/HZSM-5(4T)@γ-Al2O3 catalyst had a better catalytic activity than HZSM-5(4T)@γ-Al2O3.The active center of the reaction system of HZSM-5(4T)@γ-Al2O3 was proton,Bronsted acidic center,and that of AlCl3/HZSM-5@γ-Al2O3 could be Lewis acidic center.The source of the Lewis acidic center was the multi-center bond formed by the delocalization of peripheral electrons of the atoms.The frontier orbital theory confirmed the mechanism and good selectivity of the reaction.