This study, utilizing X-CT, obtained internal structural information of the No.3 Sacred Tree, which directly reflects its casting technology and provides a scientific basis for interpreting the technical achievements of the Sanxingdui bronze civilization. It revealed that the No. 3 Sacred Tree was not only cast as a whole in sections, but its individual components were also cast separately and then joined into a complete tree using casting joints. The production of the trunk’s clay core employed both core rod and strip chaplet techniques. The casting process of the No. 3 Sacred Tree demonstrates that Sanxingdui bronze casting possessed a sophisticated technical system and unique technical characteristics. From a casting technology perspective, the most evident manifestation is the use of sectional casting, which is consistent with the casting techniques of other contemporary bronze assemblages, although sectional casting was applied more extensively in Sanxingdui bronzes. This study identified for the first time the use of strip chaplet during the Shang period, clarifying its manufacturing method, joining technique, and functional mechanism. The function of core rods in the No. 3 Sacred Tree is consistent with that in other sacred trees. The casting process flow for the Sanxingdui No. 3 Sacred Tree was evidently meticulously planned and designed, reflecting that Sanxingdui bronze production had reached a considerably high level. Furthermore, based on the structural characteristics of the tree’s fractures, the connection relationships between components at the fracture sites were determined, providing a scientific basis for interpreting the damage patterns of Sanxingdui bronzes.

　　The internal structure of B2771-2

　　Connection sequence and distribution of core rods and strip chaplets of the No.3 Sacred Tree Trunk (Schematic Diagram)

　　The photo of the reassembled components of the No.3 Sacred Tree