Abstract: The principle and method of nondestructive inspection on tube wall thickness and defect using compton scattering are described. The wall thickness and the cavities in inner wall of steel tube versus count rate are calibrated using radiation sources ~(137)Cs and ~(60)Co. The results show that the inspection accuracy for wall thickness of Φ 100 mm× (1—6) mm steel tube is about 0.1—0.2 mm, and the inspection sensitivity for cavity in inner wall is about Φ 5 mm× 0.5 mm. The study will be of great value for practical applications.