Abstract: Yishu Basin in Jilin Province has good water-rich strata and rich geothermal resources, indicating good development and utilization prospects. Based on the existing geothermal geological survey and evaluation data of Yishu Basin, the authors in this article combed and analyzed the hydrogeological and geothermal geological conditions of the basin, combined with relevant standards, specifications and hydrochemical methods. Besides, the occurrence conditions, hydrochemistry and isotope composition of geothermal fluids in the basin were also discussed, and the geothermal reserves were estimated using the parameters of thermal storage rock mass. The conclusion shows that the geothermal fluid in Yishu Basin mainly exists in the compressed water of deep clastic rock fissures and pores, and the formation conditions have high similarity and certain homology, which are low-temperature alkaline underground hot water with high total dissolved solids (TDS), fluorine containing, metasilicic acid and chemical type of HC${\mathrm{O}}_3^{-}$-Na⁺. The composition of hydrogen and oxygen isotopes shows that the supply of underground hot water is mainly ancient precipitation, and the age of the geothermal water is 27 Ka. The geothermal fluid storage volume is 4.20×10¹⁰ m³, and the recoverable volume is 3 446.94×10⁴ m³/a. The results of this research could provide scientific basis for the subsequent management, development and utilization of geothermal resources in the area.