Experiments indicate that a catalytic amount of CuI plays an important role in the siloxane-mediated Pd-catalyzed cross-coupling reactions with the direct use of organolithium reagents. Addition of organolithium to the siloxane transfer agent generates an organosilicon intermediate. DFT calculations indicate that CuI initially accelerates the Si-Pd(Ⅱ) transmetalation of the organosilicon intermediate by the formation of CuI2 . Subsequently, CuI2 works as a shuttle between the Si-Cu(I) and Cu(I)-Pd(Ⅱ) transmetalation processes.