The origin of deep natural brine in Jianglin depression was studied for the first time. The authors detected that the natural brine is of the sedimentary origin and characterized by wide distribution and high salinity. In the sandstone, the distribution of high-salinity natural brine shows obvious regularity: the closer the natural brine to the sag or salt strata, the higher the salinity of the natural brine. The chemical composition analysis shows that the Jiangling depression is rich in brine fluid deposits which contain lots of trace elements and have higher salini- ty. The higher the mineralization intensity, the higher the trace elements content, and some elements are na- tional badly-needed mineral resources, such as K, Rb and Cs.