Abstract: Against the backdrop of increasing global energy demand and growing carbon emission pressures, the development of efficient and clean energy conversion technologies has become a major focus of scientific and engineering efforts. Hydrogen energy is regarded as one of the most promising alternative energy sources due to its high energy density, zero carbon emissions, and sustainability. Electrochemical water splitting produces high-purity hydrogen with minimal CO₂ emissions, making it an environmentally friendly hydrogen production method. However, the commercial application of this technology still highly depends on efficient and stable electrocatalysts to reduce the overpotential of the hydrogen evolution reaction （HER） and improve energy conversion efficiency. Although platinum （Pt）-based catalysts exhibit excellent HER activity, their high cost and limited availability restrict large-scale application. Therefore, developing non-precious metal electrocatalysts with high activity, stability, and low cost has become a key research priority. Among various candidate materials, molybdenum carbide shows promising potential to replace Pt due to its Pt-like d-band electronic structure and good electrical conductivity, demonstrating excellent HER performance across a wide pH range. Nevertheless, challenges such as overly strong hydrogen intermediate （H*） adsorption, active site blockage, limited surface area, and insufficient long-term stability hinder its practical application. This review systematically summarizes recent advances in molybdenum carbide-based electrocatalysts for HER, focusing on their electronic structure, synthesis methods, performance optimization strategies, and reaction mechanisms. First, the fundamental mechanism of electrocatalytic hydrogen evolution is introduced, and the potential advantages and limitations of molybdenum carbide as an HER catalyst are analyzed based on its crystal and electronic structure. Then, major synthesis strategies for molybdenum carbide are summarized, including high-temperature carbonization and chemical vapor deposition, highlighting the advantages and limitations of each method in controlling morphology, size, and interface structure. Furthermore, modification approaches for enhancing the HER performance of molybdenum carbide are discussed from multiple perspectives, such as electronic structure modulation, interface engineering, and composite construction—specifically through heterojunction formation, heteroatom doping, carbon compositing, and defect engineering. Density functional theory （DFT） calculations are employed to gain deeper insight into the catalytic mechanisms and structure–activity relationships. Finally, future directions for molybdenum carbide-based catalysts are outlined based on current challenges. This review demonstrates that rational structural design and performance optimization can significantly enhance the HER activity and stability of molybdenum carbide-based materials, providing a theoretical and technical foundation for their practical application in electrochemical water splitting. Future research should emphasize the integration of material design and mechanistic studies to facilitate the transition of molybdenum carbide catalysts from laboratory research to industrial application.