In order to solve the problems of uneven gap distribution and flow pattern in complex parts with multi-stage internal cone holes in electrochemical machining, a method of computer simulation assisted cathode design was proposed. The electric field and flow field models of machining gaps were established respectively, and the simulation of different cathode profiles was carried out. When the cathode cone angle is 2°, the electric field distribution between the cathode and the workpiece is reasonable, and the electrolyte distribution in the machining gap is uniform. With the conditions of processing voltage 10 V, electrolyte inlet pressure 1.5 MPa, electrolyte temperature 28 ℃ and cathode feed speed 5mm/min, the ECM processing of multi-stage internal cone hole was carried out by using the optimized cathode. The results show that the surface of the workpiece has no flow pattern, the dimensional forming accuracy is better than 0.1mm, and the surface roughness reaches Ra0.697µm. Research shows that the optimization of cathode structure with computer simulation can shorten the cathode development cycle and reduce the cost of cathode design effectively in ECM, which provides an efficient and feasible method for the optimization of complex cathode structure.