Fanjiayan Site is located on the second-level terrace in the west of the Diaoyucheng Fortress, which is in the arm-chair depression area, surrounded by mountains on three sides, facing the river on one side, leaning against the Diaoyu Mountain, next to Ma 'Anshan in the north, bordering Bodao Ling in the south, adjacent to the Waicheng cliff in the east, facing the Jialing River. It faces  Gaowang Mountain, Mu Mountain and Hutou Zhai across the river.Four archaeological excavations were carried out from 2013 to 2019, which had set a total of 170 excavated grids and 48 trenches, covering an area of more than 10,000 square meters. 263 sites of various types of relics from the Song Dynasty to the Qing Dynasty were tidied up during Four archaeological excavations, and more than 3,600 relics were unearthed.It has been inferred that Fanjiayan Site is a Government office in the southern Song dynasty from the comparative analysis of archaeological remains and Zicheng and Fuxie maps in local records of Song Dynasty.This government office is divided into office area and garden area. Office area consists of walls, central axis buildings and ancillary buildings while the garden area is centered on the large pool, surrounded by gate houses, pavilions, terraces, flood interception ditches and drainage culverts.The Fanjiayan site has constituted the urban defense system of the mountain, water and city, together with the previously excavated Navy Wharf, Southern Yizi City, Site of the Nine Pots, hilltop Ring City and other sites, which provides a strong support for the application of the World Cultural Heritage of the Diaoyucheng Fortress.