In this paper, the application condition of cutandcover topdown construction method is presented, with the design of the outhung hall of China Art Gallery Station of Line 8 of Beijing Metro as an example. Comparison and contrast is made between cutandcover topdown construction method and cutandcover bottomup construction method and the former is adopted for the outhung hall structure. The design idea and key design points, structural calculation and waterproofing technology of the outhung hall structure are presented. The types of the foundations under the steel pipe columns and the modes of the connection between roof slabs and side pile top beams are discussed. In the end, longitudinal bottom beams constructed in mined pilot tunnel are adopted as the strip foundation under the steel pipe columns, and fixed connection is adopted between roof slabs and side pile top beams. In this way, the problem of limited space is solved and the safety of the surrounding buildings is guaranteed. 