This article investigates the impact of dielectrics on the properties of micro-holes fabricated by micro-electrical discharge machining. Based on experiments using kerosene and deionised water as the working fluid, the machining in different dielectrics is investigated. The flow of the water is analysed by means of a flow field simulation, and corresponding experiments are also conducted to verify the simulation results. Suitable parameters are obtained to process a micro-hole array with 256 holes, a configuration widely used in printer ejector mechanisms. The average diameter of the holes is 44.47 µm, and the maximum diameter deviation is 1.3 µm.