Amodified counter-rotating electrochemical machining (CRECM) method is proposed for machining a convex array on rotary part, in which a small cylindrical cathode tool rotates in the opposite direction to and at n times the angular velocity of the anode workpiece. The trajectories of the cathode tool and the profiles of the convex structure were analyzed numerically. The electrolyte flow distributions in immersed and enclosed flow mode were simulated. The results indicated that tapered, straight, and inverted tapered sidewalls can be obtained for cathode tools with different radii, and the enclosed flow mode can give a better flow of electrolyte. Experiments were conducted using small cathode tools with different radii in a specially designed electrolyte cell. Five convex structures were fabricated on the surface of the anode workpiece using a small cathode tool with a single concave cavity. The sidewalls were near straight with small taper angles of 0.71 degrees and -0.61 degrees. Moreover, a cylindrical anode workpiece with an extensive convex array on the surface was fabricated successfully using a small cathode tool with multiple convex cavities. This indicated that the proposed method can offer a superior machining ability for the rotary part with array structures. (C) 2019 The Electrochemical Society.