Abstract: The second palace-site within the palatial city of the upper capital of Bohai State stands as the largest individual building site and ranks among the most expansive single construction sites in Sui and Tang dynasties. From the angle of architectural archaeology, this paper systematically analyzes the tiles found in the collapsed remnants of the second palace site to deduce its bay configuration, spatial arrangement, roof forms and ridge decorations. Subsequently, integrating these findings with the planar ruins, the paper accomplishes a comprehensive restoration of the site and delves into the pertinent hierarchical issues, resolving the academic debate of the fundamental form of this significant palace during Sui and Tang dynasties.