Abstract: A combined ultrasonic micro-forging device and a related additive manufacturing method for improving the microstructure and mechanical properties of additive manufactured metal part. The device comprises a transducer, a pneumatic sliding table, a pneumatic sliding table connecting frame, an amplitude transformer, a tool head and a roller, wherein the transducer is provided in a transducer housing, a socket connector and a pipeline connector are provided on the transducer housing, the amplitude transformer is connected under the transducer, the tool head is connected under the transducer, the roller is located between the tool head and workpiece, and the pneumatic sliding table is connected to the transducer housing and the amplitude transformer via the pneumatic sliding table connecting frame.