<p>The electrode feeding strategy in deep and narrow slot electrical discharge machining (EDM) is crucial for achieving reasonable electrode motion control and maintaining a stable discharge state. However, existing strategies predominantly rely on empirical values of the servo reference voltage to determine electrode advance and retraction actions, the accuracy of which requires further improvement. In practice, the inter-electrode discharge voltage is influenced by a combination of electrical parameters, inter-electrode gap width, and machining debris concentration. Therefore, the determination of the servo reference voltage should comprehensively incorporate these factors. This study systematically investigates the effects of electrical parameters, debris concentration, and inter-electrode gap distance on the discharge voltage. A functional relationship among these parameters is established, enabling the calculation of the servo reference voltage under varying electrical conditions and facilitating the formulation of a refined electrode feeding strategy. The results indicate that the maintenance discharge voltage tends to increase with larger gap distances, while it decreases with higher debris concentrations and longer pulse widths. In comparative experiments between the conventional and proposed strategies, the new strategy demonstrates superior performance, particularly in large-depth machining. It significantly enhances machining efficiency while maintaining machining accuracy.</p>