To improve accuracy of turbine blades by electrochemical machining (ECM), a new cathode’s feeding method was studied. The rational optimization rules were proposed. Based on the theory of ECM, the blade’s shape evolution was analysed. The influence of the current efficiency brought by the passivating electrolyte, and flow factors influencing the machining process were also considered. According to the rules the cathode’s feeding route was optimized. By using the three-electrode feeding ECM machine, the cathode’s feeding routes can be varied flexibly.