Abstract: For the penetrant inspection of large titanium ally casing with a diameter of 1 400 mm,the electronic spraying method can make the penetrant cover the entire surface with unnecessary liquid penetrant deposition. This method reduces the cleaning time,obtains an acceptable background and reliable defect indications. Combining black light source with industrial endoscopy can widen the reachable area of human vision in the process of penetration detection. The selection of the industrial endoscope lens used in the inspection should be based on the cavity size, the defects location and the proper lighting conditions (with suitable distance apart from the surface to be inspected) in order to obtain the clearer indication of defects and improve the accuracy and reliability of the judgment.