Equilibrium geometries, charge distributions, stabilities, and electronic properties of the Cu-adsorbed (SiO2)n (n=1—8) clusters are investigated by using the density functional theory in the generalized gradient approximation for exchange-correlation functional. The results show that the Ag atom preferably binds to silicon atom with dangling bond, and the incoming Ag atoms tend to cluster on the existing Ag cluster leading to the formation of Ag islands. Therefore the ability for Si to lose electron is weaker, while the ability for Si to gain electron is stronger. In addition, the energy gaps between the highest occupied and the lowest unoccupied molecular orbitals remarkably decrease compared with the pure (SiO2)n (n=1—8) clusters, eventually approaching the near infrared radiation region.