Objectives:The Yanqing geothermal field,as a completely independent thermal field of the ten geothermal fields in Beijing,its unclear genetic model restricts the scientific and orderly development of geothermal resources. There are three reservoirs in the geothermal field, which are Yanshanian granite, Cretaceous sandstone and Jixian dolostone, respectively. With a comprehensive consideration of geothermal geological conditions, heat flow and water flow, this paper aims at constructing a genetic model of Yanqing geothermal field. Methods:Analysis on hydro- chemistry, isotopes and thermophysical properties revealsimportant features of the Yanqing geothermal field,including the geological structure, geothermal flow, and the recharge source, age, heat storage temperature and circulation depth of geothermal fluid. Results: The heat flux of Yanqing geothermal field is 75. 6 mW/m 2. Isotopic data indicates that geothermal water is recharged from the northern mountains of Yanqing by precipitation. Three thermal reservoirs field yield different geothermal water ages and circulation depth. Ages of geothermal fluid in the Yanshanian granite, Cretaceous sandstone and Jixian dolostone geothermal reservoir are 15~21 ka, 28 ka and 48 ka, respectively. The circulation depth of geothermal water is ~2500 m in the granite and Cretaceous sandstonereservoir, but ranges from 2900 m to 3600 m in the Jixian dolostone. As the major reservoir in the Yanqing geothermal field, the ground temperature of thermal reservoir in dolostone varies between 80. 5~98. 3 ℃ with an average temperature at 90. 6 ℃。Conclusions: The Yanqing geothermal field is a non- volcanic geothermal system heated by normal geothermal heat flow. Water is recharged from the northern mountains of Yanqing with differernt thermal water ages, and then circulated at variable depths.