Aimed at fuel injection nozzles of a type of aero engine are difficult to cut with traditional machining methods because of the following problems of microsized and hard material, the principle and setup of electrochemical micromachining and device were introduced. A microrod tool electrode and a trianglehooked electrode were made. Rough machining process with layered electrochemical milling was used to remove remained material of the part, and finish machining process with swirlscanning electrochemical milling was applied to machine the full surface of the swirl chamber. The microsized swirl chamber with high precision and good surface roughness of an aero engine nozzle was achieved with electrochemical micromachining technology. Study results show that electrochemical milling micromachining is a feasible and effective method to machine microstructures of metal parts.