The present paper,discussing the significant role that the superintendency of Tianjin Customs,which was set up in 1870,had played in the negotiation between Qing and the Korean Joseon dynasty,observes that the superintendency was gradually replaced by Qing's special commercial representative with a view to strengthening Qing's suzerainty over Korea and this effort actually made Korean sovereigns and their high ministers dissatisfied and the Sino-Korean relation increasingly sour.