The developing of Chengde Area in modern ages arised under special historic backgrounds. The economic developing of this area was greatly prompted by large amounts of migrations out of the passes and the emerging of the Summer Mountain Mansion,which was the political center outside the Great Wall.The regional features and the process of economic developing in Chengde Area are studied In the two consequent stages with the clue of the rising and decli ning of summer Mountain Mansion. It is also elucidated that the declining of the Mansion had affected not only the economic development of Chengde City itself, but also the economic geographic appearance of the whole region.