Abstract: High-entropy alloys (HEAs), designed based on the multi-principal element concept, break through the traditional alloy design strategy dominated by one or two principal elements. Owing to their superior comprehensive properties, including high strength, high hardness, excellent corrosion resistance, and remarkable thermal stability, HEAs have attracted extensive attention in recent years. With the rapid development of powder metallurgy and additive manufacturing technologies, powder-metallurgy-processed HEAs have emerged as a research hotspot in the field of advanced materials. Compared with conventional casting methods, powder metallurgy can effectively improve compositional homogeneity and microstructural refinement, enable near-net-shape fabrication, and expand the capability for producing complex components. This paper systematically reviews the fundamental theories and core effects of HEAs, with emphasis on powder preparation techniques such as mechanical alloying, gas atomization, electrode induction melting gas atomization, plasma rotating electrode process, and plasma spheroidization, as well as consolidation and forming technologies including spark plasma sintering, hot extrusion, hot isostatic pressing, and additive manufacturing. Furthermore, the strengthening mechanisms and performance advantages of powder-metallurgy HEAs in terms of mechanical properties, corrosion resistance, high-temperature stability, and irradiation resistance are summarized. Their potential applications in nuclear energy, aerospace engineering, marine environments, and high-performance coatings are also discussed. Finally, future challenges and development directions, including cost reduction, process optimization, and materials genome engineering design, are proposed.