Abstract: Electrocatalysis is a technology that accelerates redox reactions between electrodes and electrolytes through the application of an external electric field. This approach offers several benefits, including environmental sustainability, high efficiency, energy conservation, diverse product output, and process controllability. It is widely applied in the fields such as electrochemical synthesis, fuel cells, water electrolysis for hydrogen production, and the remediation of environmental pollutants. However, the electrocatalytic process happened at the complex three-phase interfaces and in confined reaction environments creating by applied electric fields, which hinder the monitoring of dynamic evolution of catalyst structures during electrocatalytic reactions. This limitation significantly restricts the scientific and efficient utilization of electrocatalysis technology. Utilizing the characteristics of X-ray absorption spectroscopy (XAS), such as specific element selectivity, in situ electrochemical analysis can accurately monitor the evolution of electronic and coordination structures of catalyst active sites throughout electrocatalytic reactions, thereby providing crucial detection tools for in-depth studies of electrocatalytic mechanisms. This article begins by introducing the basic principles of XAS technology along with its in situ and ex situ testing methods, followed by a review of representative applications of in situ XAS in various electrocatalytic reactions in recent years. Lastly, we give the discussions on the prospects and challenges associated with applying XAS technology in the field of in situ electrochemistry.