To develop high energy-density micro power generation systems, a novel two-stroke cycle micro free-piston swing engine (MFPSE), inspired by the concept of the micro internal combustion swing engine, is proposed to supply mechanical power for a micro power generation system. The working principle, gas exchange and ignition timing control cycles, and structure and operation advantages of the MFPSE are discussed in detail. A prototype where the timing control and geometric parameters are designed with reference to a traditional two-stroke cycle internal combustion engine is fabricated. The successful ignition experiment shows that this new concept engine is feasible and is worthy of further study.