In recent years, In2O3 nanowires (NWs) have been widely explored in many technological areas due to their excellent electrical and optical properties; however, most of these devices are based on In2O3 NW field effect transistors (FETs) operating in the depletion-mode, which induces relatively higher power consumption and fancier circuit integration design. Here, n-type enhancement-mode In2O3 NW FETs are successfully fabricated by doping different metal elements (Mg, Al and Ga) in the NW channels. Importantly, the resulting threshold voltage can be effectively modulated through varying the metal (Mg, Ga and Al) content in the NWs. A series of scaling effects in the mobility, transconductance, threshold voltage and source-drain current with respect to the device channel length are also observed. Specifically, a small gate delay time (0.01 ns) and high on-current density (0.9 mA/μm) are obtained at 300 nm channel length. Furthermore, Mg-doped In2O3 NWs are then employed to fabricate NW parallel array FETs with a high saturation current (0.5 mA), on/off ratio (>109) and field-effect mobility (110 cm2/V•s), while the subthreshold slope and threshold voltage do not show any significant changes. All these results indicate the great potency for metal-doped In2O3 NWs used in the low-power, high-performance thin-film-transistors.