ZnO nanowire or nanorod arrays have caused great interest owing to their unique properties and versatile applications in short-wavelength lasers, electroluminescent devices, photocatalytic systems, and solar cells, etc. The electrical and optical properties of ZnO nanorod arrays can be altered and controlled through doping. In this paper, B2H6 plasma treatment was employed to improve the electrical properties of ZnO nanorod arrays prepared by hydrothermal synthesis. A clear decrease in the resistivity of ZnO nanorod arrays with B2H6 plasma treatment was observed. Moreover, the measurement results of XPS and Hall measurement show that the B2H6 plasma treatment can be used to achieve n-type doping via B atoms substitution for Zn atoms.