The redistribution method plays an important role in addressing the issue of organosilicon by-product in the direct synthesis of dichlorodimethylsilane, and the redistribution mechanism is still a topic of debate. The redistribution by ZSM-5(3T)@γ-Al2O3 core-shell catalyst and post-modified AlCl3/ZSM-5(3T)@γ-Al2O3 catalyst was technically performed using the Density Functional Theory (DFT) at the level of B3LYP/6-311++G(3df,2pd). The result shows that No.1 active site of ZSM-5(3T)@γ-Al2O3 core-shell structure has a significant effect on the activity of the catalyst. Indicating that the active center involved in the reaction is H provided by Al-O-H bond, which is an obvious catalytic active center of Bronsted acid. Furthermore, post-modified AlCl3/ZSM-5(3T)@γ-Al2O3 catalyst is in more favor of redistribution reaction comparing with ZSM-5(3T)@γ-Al2O3 core-shell catalyst. It ascribes to the robust Lewis site of aluminum chloride favorable modification.