Abstract: Hot-rolled AMS6308 steel and Q-tempered AMS6308 steel were welded on HWI-IFW-130 inertia friction welding machine, respectively. Mechanical properties and microstructures of joints were studied. For the joint welded by hot-rolled AMS6308 steel, weld zone is martensite microstructure, heat affected zone and thermo-mechanically affected zone are martensite and bainite microstructures. For the joint welded by Q-tempered AMS6308 steel, the microstructure of weld zone is the same with that by hot-rolled AMS6308 steel, while the microstructure in heat affected zone and thermo-mechanically affected zone are tempered martensite. The microhardness distribution of the joint is symmetrical with the center of weld, and the highest microhardness occurs in weld zone. All fractures occur at the base metal in tensile test.