Quaternary Linli sag is a SN-trending secondary tectonic unit in the western part of the Dongting basin, and is located between Wuling and Taiyangshan uplifts. In this paper, the authors probed into the tectonic-environmental genesis of the water system in Linli sag and the heavy minerals characteristics of sediments in ZK257 borehole in north of the sag, which provided more constrains on the Quaternary geological evolutions. All of the heavy minerals in the mid-Pleistocene Dongtinghu Formation from the ZK257 borehole derived from the pre-Quaternary sediments in the sag and its adjacent areas, indicating that the paleochannel of the Yuanshui River didn’t passed by the Linli sag. The denudation of the adjacent areas spread to lateral area with the lithologic change of sediment source when the sag expanded, thus causing that the heavy minerals contents in the upper part of the Dongtinghu Formation are higher than those in lower part.