Abstract: The oxide dispersion strengthened (ODS) copper alloy with 4 mm in thickness was joined by friction stir welding (FSW) to investigate the basic characteristics and feasibility of FSW technology of ODS materials. The microstructure and mechanical properties of ODS-Cu joint were studied. The microstructures of welded joint consist of four parts: weld nugget zone(WNZ),thermo-mechanically affected zone(TMAZ), heat affected zone(HAZ) and base material(BM). The boundary of the TMAZ and HAZ in advanced side is clear, while it is blurred on the retreating side. The WNZ is composed of fine equiaxed recrystallized grains and onion rings structures and "L" line is observed. Deformed grain is distributed along a certain direction in TMAZ, while the grain coarsens slightly in HAZ. The micro-hardness along the weld cross-section shows V-shaped distribution and the hardness of WNZ is the lowest.