Abstract: When X-ray test was performed on the single crystal turbine blades of a certain type engine, there is an indication of suspected foreign objects on the film. In order to find out the cause of foreign objects, we cut a blade and through energy spectrum analysis we found that there was no significant difference on material element content between foreign objects and the blade. It was indicated that the metal-powder produced in the grinding process entered the blade cavity through the inlet and exhaust holes in the blade, and during brazing of the leaf crown assembly surface, the powders were bonded to the inner wall of the blade in the vacuum brazing furnace at high temperature.