Abstract: Superalloy closed impeller has complex structure with multi-layer, thin-walled, curved inner chamber connected with larger diameter journal. When it is tested by traditional X-ray radiography, there are some problems such as X-ray can not penetrate the thick area of impeller and defects can not be located. Therefore, high-energy X-ray industrial CT testing method is used. In order to verify the defect detection ability, the artificial holes of known sizes were machined on the closed impeller to be tested. The result shows that the holes of φ0.5 mm can be detected. By detecting the actual defects in the closed impeller, the internal defects such as pore and shrinkage can be detected and located.