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Screw drill is one of the most widely used power drilling tools in the field of deep sea drilling because of its excellent performance such as low drilling speed, high torque, and strong overload capacity. However, it has the problems of complex internal structure and long processing stroke of screw drill stator. In this paper, the electrochemical machining (ECM) technology is used to solve the problem of internal spiral curved surface special-shaped deep hole machining. Firstly, the initial cathode structure with spirally increasing tooth surface of six machining teeth is designed, and the gas-liquid two-phase flow field model of the gap is established to simulate and analyze it. The simulation results show that the flow field distribution of the electrolyte in the machining gap is not uniform and the bubble concentration is high. Secondly, the initial cathode structure is optimized by adding different numbers of liquid-increasing grooves on the tooth surface of the machined tooth, and the gas-liquid two-phase flow field is simulated. The simulation results show that the cathode structure with four additional baths on each tooth surface results in a better overall flow of electrolyte in the machining gap, a flow rate of more than 3 m/s in the machining area, and a significant reduction in the concentration of electrolyte bubbles, with a reduced rate of 18.7% and a smaller distribution area for the highest bubble concentration, ensure the machining accuracy. Finally, the orthogonal experiment of 4 factors and 4 levels was designed, and the optimized processing parameters were obtained by gray correlation analysis method, that is, inlet pressure of 0.4 MPa, machining voltage of 11 V, duty cycle of 40%, and cathode feed rate of 0.9 mm/min, under which the deviation of the large end diameter of the deep special-shaped hole was 0.15 mm, the surface roughness of the inner wall of the hole was 0.487 μm. The data shows that this combination of processing parameters meets the production requirements of the product. The data shows that this combination of machining parameters meets the production requirements of the product. The COMSOL simulation method significantly shortens the research cycle and saves research costs. [ABSTRACT FROM AUTHOR]