The Lianhua Mountain area in Yingjiang county，Yunnan province，is one of the several w regions in Yunnan that contains medium-high temperature geothermal resources. Previous geothermal research was more focused on meeting the actual production needs, lack of the in-depth exploration in aspects such as the sources of geothermal water chemical components，water-rock interactions，multi-method evaluations of reservoir temperatures，and the genetic mechanisms of geothermal systems. Based on hydro-geochemical methods，this paper aims to identify the circulation process of geothermal water and clarify the formation mechanism of the geothermal system. Through mathematical statistics and correlation analysis of hydrochemical indicators，Piper diagrams，Schoeller diagrams，diagrams of the relationships between anions and cations，hydrogen and oxygen isotope analysis，SiO₂ geothermal temperature scale，and the multi-mineral equilibrium method，a systematic study was carried out on the geothermal water chemical types，sources of major ionic components，recharge sources of geothermal water，reservoir temperatures，and circulation depths in the Yingjiang basin. Subsequently，the origin of geothermal water was inferred. The results show that the hydrochemical type of the geothermal fields in the Yingjiang basin is HCO₃-Na type. The major ionic components in the geothermal water originate from the dissolution of halide minerals，feldspars，fluorides，gypsum，and other minerals，and are influenced by cation-exchange reactions. The geothermal water is mainly recharged by mountainous atmospheric precipitation at an altitude between 1 348-1 571 m. The deep reservoir temperature is 168.2 °C. During the upwelling process，the geothermal water undergoes water-rock interactions and cation-exchange reactions with the surrounding rocks，resulting in the changes of its hydrochemical components. The heat source of the reservoir mainly comes from the magma chamber in the deep crust. Part of the heat is transferred upward in the form of heat convection through the connection of the Sudian-type fault zone，and the other part is transferred upward through rocks in the form of heat conduction. Atmospheric precipitation infiltrates and circulates along the water-conducting structure，absorbs the heat transferred upward by the magma chamber，and heated. Eventually，a convective-conductive composite hydrothermal system dominated by HCO₃-Na type water formed near the fault zone.