Piece-mold casting was a unique means for bronze manufacture in ancient China, and cast-on was a kernel technique for big and sophisticated objects. Nevertheless, it was ignored till the middle of the 20th century since R. Gettens recognized cast-on in the Freer Gallery of Art by cutting first and then through X-radiography, even though the later method was limited by object shapes. Industrial computed tomography (CT) employed to examine Chinese bronzes since 1980s, which has not only broken through the limitation but also contributed more discoveries. A series of phenomena such as ring-shaped tenons, pins and welding, etc. in cast-on have been discovered by CT examinations in both Japan and China. This paper briefly reviews the history of studying the cast-on of Chinese bronzes including the changes of methodologies, reveals the value of radiography and emphasizes the importance of problem consciousness as well as creative theory, method and facility.