Variation features for seasonal drought/flood over the Hanjiang River Basin have important climatic meaning because of its special geographical location. The study basin is located in the south-north transitional zone of geography and climate in China, as well as the starting point of the Middle Route of South-to-North Water Transfer Project in operation. In this paper, data sources were historical documents including records from a unique historical archive named Yu-Xue-Fen-Cun and collections from local gazettes and other historical information. A total of 31752 records according to different time resolutions, districts, record classes from 1736 to 1911 were collected from Yu-Xue-Fen-Cun archive with about 179 records yearly, and 2542 records from 1735 to 1911 were collected from other historical documents with about 14 records yearly. Based on the features of historical documents over the Hanjiang River Basin, methods with 3 standards of spatial distributions, severity and duration were put forward as the way for reconstructing seasonal drought/flood grades over the Hanjiang River Basin. And then drought/flood grades for 7 prefectures in the basin in spring, summer, autumn and winter were reconstructed for characteristic analysis in the study area during 1735-1911AD. The results showed that: 1) Compared with other prefectures in the Hanjiang River Basin, there were more drought events in Shaanxi province and Nanyang prefecture in spring, summer and winter, while there were more drought events in autumn and more flood events in spring and summer in Hubei province. 2) More obvious fluctuations existed in the drought/flood grades in summer and autumn, while less existed in spring and winter. 3) For the whole basin, more flood events occurred during the 1820s-1840s, and more drought events happened in the 1850s and 1870s. 4) More successive drought seasons with greater severity were observed in the study basin in the 19th century; and most successive flood events with serious severity occurred in summer and autumn. This study has certain value for quantitative climate research in the Hanjiang River Basin, and also can provide data support for future precipitation variation research in the study area.