Carnallite is discovered in Paleocene Jiangling Depression by thin section identification and XRD analysis. The thickness of single layer can be up to 23cm, in which the carnallite content is 1.6% according to chemical analysis. There are two types of carnallite occurrences in Paleocene Jiangling Depression: for the first type, carnallite is included in halite in granulous with grain size of 0.1~0.5mm; for the other type, carnallite is filled in pore of anhydrite with grain size of 0.1~0.2mm. Through the thermometry of fluid inclusion with halite, carbon and oxygen isotopes and element geochemical study, it proposes that the paleoclimate of Paleocene Jiangling Depression is “warm and drought” type. Jiangling Depression is small rift basin in Paleocene, in which the sedimentation is large in tectonic stage; the basin is well closed and contemporaneous volcanic activity is frequent, which provide abundant metallogenic material. The warm spring after volcanic activity also provide abundant metallogenic material. Part of rift valley is connected with ocean, which provide sources for rift valey. The combination of tectonic condition, source material and draught climate in Paleocene leads to the sedimentation of carnallite. The discovery of carnallite in Paleocene Jiangling Depression reveals that the brine of Jiangling Depression has evolved to the stage to separate out potash, which has great significance to find potash.