The karst geothermal reservoir is one of the two main reservoirs for space heating in northern China.Among them，the piedmont karst reservoir is mainly located in the buried karst distribution area in the lower reaches of the karst groundwater flow system, which belongs to the discharge area of a regional groundwater flow system with deep circulation, weak opening and slow runoff. Taking the karst geothermal reservoir of northern Jinan as an example, based on the geological structure, isotopes and hydrogeochemical characteristics, this paper reveals the origin and evolution of geothermal water, as well as its migration and enrichment mechanism: a minor amount of geothermal water comes from the meteoric precipitation infiltration recharge in the distribution area of igneous and metamorphic rocks at the north wing of Taishan Mountain, while mostof it comes from the deep circulation runoff recharge of karst groundwater in the distribution area of carbonate karstfissure aquifers in the Cambrian Changqing Group and CambrianOrdovician Jiulong Group. The geothermal water mainly concentrates in compound areas between interstratified karst and fractured zone, and interlayered karst and magmatic rocks. According to the heat source and its transfer and aggregation characteristics revealed by the spatial distribution features of geothermal temperature field, the heat accumulation mechanism of four heat sources is proposed: thermal accumulation of blanket shaped terrestrial heat flow conduction, thermal accumulation of high thermal conductivity diffluence at uplift area,belt shaped convective thermal accumulation at fault zone or contact zone, and conductiveconvective thermal accumulation through groundwater transport. On the basis of the genetic mechanism of heat accumulation and water enrichment, this paper establishes the metallogenic model of karst geothermal reservoir based on the water sources, heat sources and the occurrence rule of geothermal reservoirs, the prospecting model of how to find geothermal water enrichment and heat flow accumulation areas; reveals as well as the metallogenic rule of geothermal resources and provides a basis for the exploration and prospecting of geothermal resources.