<p>The liquid hydrostatic bearing oil cavity is hexagonal and distributed on the inner surface of the bearing, belonging to a complex inner cavity curved surface structure with high machining accuracy requirements, posing a significant challenge to traditional machining processes. This study is the first to investigate the electrochemical machining (ECM) of hydrostatic bearing oil cavities and aims to investigate the effects of machining voltage and cathode liquid-through groove (LTG) size on the machining quality. Using simulation software, various physical field distributions during the electrochemical machining were simulated and experimental studies were conducted. Results indicated that enlarging the cathode LTG size improved electrolyte flow rate in the machining zone, facilitating timely electrolyte renewal and promoting uniform current density distribution. However, excessive LTG sizes not only led to reduced oil cavity surface roughness but also caused significant residual protrusions, thereby increasing post-machining finishing efforts. Elevated voltage intensified electrochemical reactions, resulting in gradual temperature rise and hydrogen evolution at the cathode, both of which negatively affected current density uniformity. Furthermore, dimensional deviation of oil cavities showed a positive correlation with increasing voltage, whereas surface roughness initially decreased and then increased with higher voltage. This study offers novel insights into the ECM of intricate oil cavities by developing a sophisticated multi-physics model. The investigation of the trade-offs between LTG dimensions and voltage nonlinearity, as well as flow field uniformity and residual protrusions, provides valuable new perspectives for the precision machining of high-performance components.</p>