Abstract: With the rapid development of renewable energy generation technologies, electrocatalytic conversion of small molecules such as H₂O, CO₂, and N₂ has demonstrated broad application prospects in clean energy production and high-value chemical synthesis. Electrocatalytic technology can convert intermittent renewable energy sources such as solar and wind power into storable chemical energy such as H₂, carbon-based fuels （e.g., CH₄, CH₃OH）, and nitrogen-containing compounds （e.g., NH₃）, and represents an important technological pathway towards the goal of “dual carbon”. However, the complex multiphase reaction processes in electrocatalytic systems involve strong coupling effects across multiple physical fields including electrochemistry, mass transfer, and heat transfer, making it difficult for traditional experimental methods to fully elucidate their intrinsic mechanisms, which limits the further development of electrocatalytic technologies. Finite element numerical simulation can be utilized to describe and optimize electrocatalytic systems based on experimental data, with the advantages of high accuracy, fast calculation speed, and intuitive solution process. The purpose of this paper is to introduce the advantages of finite element numerical simulation and to present recent advances in finite element numerical simulation in the field of electrocatalytic systems of energy-related small molecules. This paper reviews the progress of research in three key areas: catalyst structure design, reaction condition control, and reactor design. Finally, the prospective development direction of finite element numerical simulation in the field of electrocatalytic systems is prospected. Finite element numerical simulation is evolving from an auxiliary analysis tool to an important driving force for the optimization of electrocatalytic systems. With the advancement of computational methods and multidisciplinary cross-fertilization, finite element numerical simulation is expected to play a greater role in the analysis of proton-coupled electron transfer mechanism, industrial-scale electrolyzer scale-up and other key issues, accelerating the practical application of energy small molecule electrocatalytic technology.