Commercial nonsupported Cu-based catalysts have to be mixed with various promoters to enhance their catalytic performance in the Rochow-Müller reaction. However, considerable debates still exist at a fundamental level on how these promoters function. Herein, we systematically investigated the effects of ZnO, Sn, and P promoters on the catalytic property of the CuO/SiO2 catalyst for synthesizing dimethyldichlorosilane (M2) via the Rochow-Müller reaction. A series of CuO/SiO2 catalysts containing these promoters were prepared by the ball-milling method. The CuO/SiO2 catalyst with the coexistence of ZnO, P, and Sn promoters showed the highest catalytic activity, even superior to the commercial nonsupported Cu-based catalysts. Detailed characterizations showed the increased capability for oxygen adsorption on the CuO surface and dissociative chemisorption of methyl chloride led to the improved catalytic performance. This work deciphers the promoter mechanism and demonstrates a promising strategy for the efficient synthesis of M2.