Metallocenes can be encapsulated inside the carbon nanotubes. The structural, energetic and electronic properties of organometallic MCp2@SWCNT are obtained from DFT method. We verify that such encapsulation is noncovalent functionalization, and examined binding energies and charge transfers of MCp2@(16, 0)SWCNT systems. Consistent with recent experimental findings, the optimal distance between FeCp2 center and near tube-wall is 4.7 (5.1) angstrom for the configuration where MCp2's fivefold axis is parallel (vertical) to nanotube axis, while the minimal diameter is 9.4 (10.2) angstrom to exothermically encapsulate FeCp2 molecules. Finally we clarify the doping effects near the band gap by encapsulations of CoCp2 and NiCp2. (C) 2011 Elsevier B. V. All rights reserved.