Qianjiang depression is one of the important Paleogene potassium bearing brines deposits. Based on detailed field geological investigation, two dimensional and 3D seismic interpretation, logging interpretation and chemistry analysis, this paper studied the reservoir characteristics, brines forming regularity, geochemical characteristics and deposit genesis. Potassium rich brine occurs mainly in the Qianjiang Group with an area of 1630 km2. The hydrochemical type of brines is mainly sodium sulfate subtype, with salt water system of Na, K//Cl, SO4 H2O, and is secondarily calcium chloride type, magnesium sulfate subtype and carbonate type. The average salinity of brines is 280.94 g/L and pH value is between 9 and 5. The reservoir of brines is sandstone, thus the distribution of brine is mainly controlled by the distribution of sandstone body. The burial depth of the brines group floor shows the distribution feature of “one depression with two slope”, and the cumulative thickness of the brines ore body is gradually thinning from north and south. It center on syncline along the east west direction, the cumulative thickness has gradually increased to the east and the west. The brines distribution is closely relatecl to ancient landform of depositional period on the plane. The brines salinity is maximum in Banghu, Wangchang and Zhouji that are the settlement center of syncline, and the contents of KCl, B2O3, LiCl and Br are relatively higher, which reaches the grade for comprehensive utilization.