Electronic structures of 1 x 1-Au/Si(111) systems have been calculated by the ab initio pseudopotential method in a local density approximation. Au and top-layer Si produce the bonding and a large charge transfer is seen from Si to Au. Comparing the results with and without on-top Si layer, it is shown that which Si layers release the charge depends on the number of surface Si dangling bonds. The relation between the charge transfer and the change of bond strength has also been clarified.