The transmission, negative refractive index (NRI) and figure of merit (FOM) of metal-dielectric-metal (MDM) sandwiched metamaterial, which is perforated with different length of rectangular holes, are numerically studied. The low-frequency transmission peak and maximum transmission peaks of rectangular hole are red-shifted with the increasing of the length of holes. The NRI and the frequency bandwidth of NRI of the rectangular holes are reduced with the increase of the length of holes. It becomes possible to obtain a higher transmission or NRI of metamaterial by adjusting the length of the rectangular holes on MDM metamaterial arrays.