<p>High-entropy alloys (HEAs) represent a novel class of materials with exceptional comprehensive properties but often present challenges for conventional machining techniques. Electrochemical jet machining (EJM) is a modern electrochemical machining variant with numerous merits, offering a promising alternative for machining HEAs. This study is the first to investigate the high-rate anodic dissolution behavior and EJM characteristics of HEAs, using Al_0.7CrFeCoNi as a representative material. Polarization analysis and surface characterization reveal the typical active–transpassive transition behavior of this HEA in NaCl electrolytes, leading to a notable surface smoothing effect at high current densities. In contrast, the dissolution kinetics in NaNO₃ electrolytes remain partially charge-transfer controlled even at high current densities, resulting in relatively rough surfaces. Current efficiency measurements show an apparent increasing trend with current density in NaCl electrolytes, whereas the efficiency remains relatively stable in NaNO₃ electrolytes. This difference is further confirmed through a comparative analysis of the EJM material removal patterns, highlighting the superior machining localization with NaCl electrolytes. Upon these electrochemical insights, machining experiments elucidate the influences of key process parameters and their underlying mechanisms in EJM of this HEA using NaCl electrolytes. The demonstrated parametric effects are consistent with the established EJM theory. Typical surface features, with a clear profile edge and smooth surface, are successfully achieved on the HEA using the selected process parameters, demonstrating the micro-machining capacity of EJM for the HEA. These findings contribute to the advancement of EJM by extending its applicability to new material classes while offering a viable solution for machining HEAs.</p>