The Sichuan Basin is a well known large scale sedimentary basin in China with abundant subsurface brine resources. K rick brines were found in the Chuan 25 well in the northeastern part of the basin. The occurrence and enrichment of groundwater in the Triassic carbonates in the high and steep fold zone in the eastern Sichuan Basin are examined in this paper, and hydrochemical characteristics and genesis of the deep formation brines in the Chuan 25 well and Wo 57 well and the Xiannvshan hot spring and Tongji hot spring are also discussed. The results show that if the Triassic formations in the core of the anticlines are deeply buried and are in a sealed state, the subsurface brines are found to be enriched, and high TDS brines are not preserved in the Triassic carbonates in the core of the open semi open anticlines, where the carbonates outcrop due to strong weathering and erosion and infiltration and lixiviation of precipitation occur. The subsurface brines, which are regarded as connate sedimentary brines, are of Cl Na type and are rich in Br-, Li-, Sr2-, I-and B3+. The brines in the Chuan 25 well has high TDS of 352.693 g/L (close to that of the Yellow Sea water and the South China Sea water when evaporated to the stage of epsomite precipitation) and high contents of K+ of 25.955 g/L. The Xiannvshan hot spring and the Tongji hot spring are of SO4 Ca type and have relatively high concentrations of Sr2+, F- and H2 SiO3 The stable isotopes of δ2H and δ18O of the water samples suggest that the subsurface brines are of palaeo marine origin and the hot springs were meteoric in origin. Groundwater were recharged from infiltration of precipitation in the outcropping areas in the cores of the anticlines and obtains heat when undergoing deep circulation and emerges as a hot spring in the low river valleys. The hot water has TDS of 2~3 g/L and forms after lixiviation of groundwater in the carbonates. As a result, the hot water has a tendency of becoming fresh.