The electronic and magnetic properties of the recently synthesized A-site-ordered perovskites A'Cu3Sn4O12 with A' = Ca2+, Sr2+, and Pb2+ were investigated by use of the density functional theory. The results indicate that the ground states of them are all ferromagnetic insulator and the magnetic properties are determined primarily by the direct ferromagnetic interaction between A-site Cu2+ ions, which is consistent with the available experimental results. By replacing bivalent A' ion by trivalent La ion, we found that the electron is injected into A-site Cu and LaCu3Sn4O12 is predicted to be ferromagnetic half-metallic. (C) 2010 Elsevier B. V. All rights reserved.