The Jiyang North Geothermal Field is located in the geothermal area of the Northwest Depression of Shandong Province, hosting abundant low-to-medium temperature geothermal resources with relatively limited research. Hydrogeochemical analysis of geothermal fluids can reveal the source and evolution process of geothermal water, ang elucidate the genetic mechanism of the geothermal system. The results indicate:The chemical type of sandstone geothermal reservoir water in the area is Cl-Na type.Ions in geothermal water mainly originate from the dissolution of salt rocks and carbonate rocks, with water-rock interactions not reaching equilibrium.Geothermal water is recharged by atmospheric precipitation from the southern Taishan Mountain range, with a recharge elevation of 700~900 m.Reservoir temperatures range from 72.50~89.80 ℃, while deep geothermal water temperatures reach 88.84~109.13 ℃, with a cold-water mixing ratio of 38.5%~48.7%.Geothermal fluid circulation depth is 1 628~2 120 m.The study area exhibits a sedimentary basin-type conductive-convective composite geothermal system, where near NS-and NE-trending faults form local upward channels for geothermal water. During deep circulation, water-rock interactions with surrounding minerals generate Na⁺ and Cl^- dominated geothermal fluids.