Based upon the Landauer formula,we have studied electron transport properties of finite incommensurate and commensurate double_walled carbon nanotubes(DWNTs).The results obtained show that the geometrical structures of the tube may produce significant effects on their electron transport properties:Electron transport of the incommensurate DWNTs may be either ballistic or non_ballistic,depending on the energy region.The commensurate DWNTs formed by the armchair tubes may displa y quick and slow oscillation;however,those formed by the zigzag tubes have no re gular slow oscillation.