The invention relates to a device and method for preparing spherical titanium powder and titanium alloy powder through gas atomization, which belongs to the field of powder metallurgy industry. The device comprises a vacuum chamber, a continuous feeder for titanium or titanium alloy wires/rods is arranged outside the vacuum chamber, a dynamic sealing device is arranged at the top of the vacuum chamber, a metal straightening device is arranged inside the vacuum chamber, an atomizing chamber is arranged below the vacuum chamber, a gas atomization nozzle is installed between the atomizing chamber and the vacuum chamber, the center hole of the nozzle is internally provided with a wire/rod guiding device, a high-frequency smelting coil is installed below the nozzle, wherein the dynamic sealing device, the straightening device, the guiding device and the high-frequency smelting coil are installed on the same axis; a heat dissipation cover is installed inside the atomizing chamber, a protective cover is arranged at the top of the heat dissipation cover, and the centers of the heat dissipation cover and protective cover and the center of the high-frequency smelting coil are on the same axis; a powder collecting pot is arranged below the atomizing chamber. By means of controlling the diameters of the wires, the atomizing gas pressure and the power of a high-frequency power supply, titanium and titanium alloy powder with different particle sizes and particle size distributions can be obtained.