Abstract: The joint of 2219 aluminum alloy and 1Cr18Ni9Ti rotary body was connected by inertial friction welding technology. The microstructure and defects of the welded joint were analyzed by SEM and EDS. The results showed that the lamellar microstructure parallel to the weld interface formed on the side of the aluminum alloy, including equiaxed fine grain area formed by dynamic recrystallization and deformable grain area elongated along the direction of frictional shear. There were holes near the outer edge of the aluminum alloy side, Cu and O elements segregated around the holes. Brittle intermetallic compounds and oxides would cause stress concentration, hinder metal plastic flow and reduce joint performance. An intermetallic compound layer about 2 μm thick formed at the interface.