To release electrolysis products and refresh electrolyte greatly within a machining gap, a welding preparation process of Micro Nested Hollow Electrode (MNHE) for micro electrochemical machining (ECM) was researched. The flow characteristics of the MNHE were simulated and analyzed to optimize its length, then, the performance test and machining experiments for the MNHE were performed. The MNHE was prepared through threading, bonding, nested size & position adjusting and welding process. The front section of the MNHE was machined into a inner diameter of 65 μm, an outer diameter of 130 μm and a length about 3.25 mm, while its rear section was convenient for clamping and connectivity. The flow rate for outlet of the MNHE could reach up to 10 m/s under fluid supplying pressure of 1.15 MPa. Finally, experiments on micro ECM holes were carried out by utilizing the prepared hollow electrode. Micro holes with the minimum inlet diameter of 157 μm and outlet diameter of 133 μm were achieved on 0.5 mm thick stainless steel. A micro T-shaped groove with 554 μm length, 160 μm width, and 224 μm depth was also milled. Experimental results indicate that the MNHE effectively improves the flow characteristics of the electrolyte within the machining gap, and it is suitable for electrochemical machining of micro structures with high aspect ratio for its easy clamp and reliable connectivity/conductivity, .