This article mainly introduces the Allotment Agreements (in Taiwan) as a kind of historical document, and how to use them to research the social history. The information might include population of each family, development of the family, things would be considered as the family properties, Family relations like family members and the inherited rights, assignment of the family property, and so on. On the other hand, the same information could also help us to understand the social status at that time, such as economic prices, social customs, and living environment. In summary, this article suggests that (1) the allotment agreements included rich historical information; (2) this information guides us to research the family history and the social culture in Taiwan under Qing Dynasty rule.