In micro electrochemical machining (micro ECM), side-insulation of tool electrode can significantly improve the machining accuracy, especially for high aspect ratio structures. This paper presented a new side-insulation approach for not only micro single electrodes but also micro array electrodes, in which spin-coating and room curing are used to coat the micro tool electrodes with a very thin film of polymer, followed by an end-rubbing process to remove the insulation material from the electrode end surfaces. Processing parameters of spin-coating were optimized experimentally, and side-insulated micro single electrodes with a double-layer epoxy coating of 3m thickness were prepared. Experiments were made to test the performance of the side-insulation film under simulated micro ECM conditions. And the results demonstrated good insulativity and high adherence strength in a 6-hour durability test. Also side-insulation for micro array electrodes was performed using this approach.