Abstract: High-entropy alloys, leveraging the four core effects—high entropy, lattice distortion, sluggish diffusion, and cocktail effect—possess advantages such as high activity, excellent selectivity, corrosion and heat resistance, and structural stability, effectively compensating for the scarcity and high cost of traditional noble metal catalysts. This paper systematically reviews various mainstream preparation techniques, including mechanical alloying, carbothermal shock, and rapid moving-bed pyrolysis, analyzing the merits, drawbacks, and applicable scopes of each technology, among which continuous synthesis techniques lay the foundation for industrial application. At present, high-entropy alloy catalysts have been widely applied in three major fields: electrocatalysis, photocatalysis, and thermocatalysis. They exhibit outstanding performance in reactions such as hydrogen evolution, oxygen evolution, CO? conversion, and organic pollutant degradation, with some materials already surpassing commercial noble metal catalysts. The study also points out existing challenges in this field, including the lack of systematic theories for alloy design, unclear catalytic mechanisms, insufficient stability under complex operating conditions, and cost and process bottlenecks in large-scale preparation. To address these challenges, this paper proposes a development approach that optimizes material design and synthesis by relying on computational materials science and advanced characterization techniques. In the future, with continuous technological iteration, high-entropy alloy catalysts are expected to achieve large-scale industrial application in areas such as hydrogen energy, fuel cells, and greenhouse gas valorization, thereby contributing to the green development of the energy and environmental industries.