The production and trade of metals was an important part of the Chinese market system in the Qing period． With a special focus on the crisis of 1766-1779，this article investigates the supply，scale，price and usage of copper in Hankou in the mid-Qing period based on historical archives． The study shows that the amount of copper in Hankoumarket was one million to two million jin ( 600-1200) in the mid-Qianlong period ( 1736-1795) ． The major demand for copper was to meet the growing needs of the handicraft industry． The fact that this copper mainly came from illegal mines in Yunnan demonstrates the scale of the illegal copper trade． Illegal copper from Yunnan became legal copper in Hankou which meant that there was a certain balance maintained between marketable copper for utensils and thegovernment procurement for the minting of cash． The existence and development of the Hankou copper market not only proves there was a uniform national copper market but also shows that the requirement of the development of China's economy for free national metal market at that time．