Abstract: Based on the comparison of isotope test results of five hot springs in Lushan County of Henan Province, the basic characteristics and genesis of geothermal field are analyzed for further identifying the conditions of geothermal resources, as well as rational development and utilization. The δD and δ¹⁸O values of hydrogen and oxygen stable isotopes of the geothermal fluid from upper to lower reaches are gradually increasing generally. Based on the composition change of hydrogen and oxygen stable isotopes, it is concluded that the recharge source of geothermal fluid comes from atmospheric precipitation, and the recharge elevation is 1 070-1 440 m estimated by elevation effect, with the recharge source area ranging from western Lushan County to the mountainous area of southeastern Songxian County. The value of radioisotope T in one of the samples is 1.4±0.8 TU, while that of other six samples are all less than 1.0 TU, indicating that the geothermal fluid is dominated by composition of fossil water before 1952. The radioisotope ¹⁴C age analysis results show that the modern carbon in sample R3 accounts for 13.00±1.18% and that in sample R7 29.68±0.97%, reflecting that sample R7 is mixed with partial modern carbon. The generation age of geothermal fluid is 12.12-15.52 ka calculated by the percentage of modern carbon in sample R3.