This paper, for the first time examines bronze objects of Sanxingdui using industrial Computerized Tomography (CT) and discuses relevant technique issues together with the evidence from the surface observation. It is pointed out that multiple pouring and various joining techniques had been widely practiced. Different parts were mechanically connected with each other by a sequence of pours, which had been the crucial technique for the casting complicated objects such as the bronzes trees. The cast on cramp device in the sunlike objects and the combination of tenon and dowel in the tree branches are typical practices of the Sanxingdui foundry. Core rods are identified in the inner cores of branches of bronze trees, most of which were likely to be made of wood or bamboo. This is the earliest evidence for the using of core rods in ancient Chinese bronzes. It is also revealed that the animal heads in some of vessels were cast in one pour together with the body by combining separate sets of molds assemblage with the main one, which left blind cores in the animal heads. This observation implies the possible variation of chronology and technical traditions of the Zun and Lei vessels unearthed from Sanxingdui.