Abstract: The spool compressor rotor is made of some GH 4169 high-temperature discs which were combined by inertia friction welding.Each inertia friction welded joints must be inspected to ensure its quality. By the research of reference reflector and special fixture, R/d Tech ultrasonic immersion inspection system is used to check the welded joints and it is proved the phased array technology applying to the inertia friction welded joints is available and reliable.