The twelve water animal sculptures around the inside of the Pan(water vessel) of Zi Zhong Jiang can circle around 360° without being detached. The piece represents an extraordinary example of bronze fabrication craftsmanship. In order to unveil the unique techniques used for its construction, computed tomography(CT) technology was applied to study the structure of the connection between the main body of the vessel and the water animal sculptures, namely the scrambling dragon decoration over the rim of the mouth, the tigershaped legs and the handles. The results show that the water animal sculptures are connected to the Pan thanks to two types of rotational axes:one is a cylinder with cap piece,and the other has a cylindrical lower part, a protruding disc form in the middle, and a cone top coinciding with the cavity inside the spine of the animal sculpture. The scrambling dragons and tigershaped legs were cast separately with protruding rods as castin inserts, which permit invisible and firm junctions to the vessel. By contrast, the solid handles were cast together with the vessel. As revealed by the XCT analysis of the Pan of Zi Zhong Jiang, the ancient Chinese artisans successfully made innovative use of the excellent mouldcasting techniques learnt from their predecessors. From an aesthetical point of view, this design concept has given the vessel a complicated yet harmonious aspect; and the attention paid to practicality and convenience has led to a reasonable and intelligent fabrication strategy. Precise determination of the complicated internal structure of the vessel has also demonstrated that the XCT technology can be widely applied in the studying of ancient bronze techniques.