Abstract: The physicochemical properties of the metal powders directly determine the forming quality of 3D-printed metal components. Metal powders with high sphericity and high purity is critical for promoting the industrialization of metal 3D printing. The powder-making principles of five mainstream powder preparation technologies were systematically reviewed in this paper, including vacuum induction-melting inert gas atomization (VIGA), electrode induction-melting inert gas atomization (EIGA), plasma atomization (PA), plasma rotating electrode process (PREP), and radio-frequency plasma spheroidization (RFPS). The technical advantages, application characteristics, and existing bottlenecks for each process were investigated from the perspectives of powder purity, sphericity, and fine powder yield. The VIGA process features low cost and wide alloy adaptability, but suffers from high impurity content and insufficient fine-powder yield. EIGA and PREP can produce high-purity powders and are suitable for high-value-added materials, such as titanium alloys and refractory alloys, but the production costs are relatively high. Plasma atomization delivers the excellent fine-powder yield, which is restricted by foreign patent barriers. Radio-frequency plasma spheroidization is mostly applied for powder modification and recycling of spent printing powders. At present, there is still a gap between China and foreign countries in the preparation of high-end fine powders and powder-making equipment. In the future, the efforts should be made to increase the yield of 15~53 μm fine powders, develop low-oxygen and high-purity powder preparation technology, accelerate the independent research and development of high-end powder-making equipment, and promote the high-quality development of the metal 3D printing materials industry.