The 1721 contract, drawn up by the aboriginal heads of the Xiadanshui she 下淡水社, was significant in that it illustrates a turning point in the early history of Qing Taiwan. John R. Shepherd cites this document as signifying the beginning of the collection of large-rent by aboriginals, due to the amount recorded in the contract being close to the average collected by Han proprietors of nearby land. Ka Chih-ming 柯志明, on the contrary, rejects this point and asserts that it was the local magistrate who, being more concerned with bureaucratic obligations, made the decision to exclude the Han cultivating household (kenhu 墾戶) from the land-tenure system and deliberately require the Han tenants to pay a higher rate of large-rent to the aborigines directly. The magistrate did so because he wanted to secure the income of the aborigines, so that aboriginal taxpayers would not avoid paying the majority of their taxes. In other words, the magistrate’s chief concern was to avoid failing in his duties. This paper finds that the contract and the local gazetteers of the 1710s reveal very similar social pictures. By providing their own labor and capital, the Han tenants not only turned wasteland into paddy fields, but through the process of land development also strengthened their control over the land and society. As a result, their rights to the land evolved into a partial right commonly called tiandi 田底, the subsoil land right. Such a right was tradable, inheritable, and immune from any interference by the proprietors of the land. By contrast, the rights of the proprietors dwindled to the right to collect rent at a fixed rate. The local officials were aware of such a tendency, but nevertheless the subsoil land rights held by the Han tenants gradually matured and became a common land tenure practice. It is not difficult to imagine how their influence gradually solidified and grew stronger as, over the generations that followed, they continued to settle the region, and invest in working and improving the land.