Lithium-potassium ores are mainly distributed in Qinghai, Tibet, Lop Nur salt lake and western Sichuan, but it is expensive and difficult to develop these ores to meet the needs of industrial development. The exploration of Jitai basin in Jiangxi Province shows that the concentration of lithium chloride in brine exceeds 600 mg/L, and the content of potassium chloride is close to 1%, which is close to or even higher than the industrial grade with high comprehensive utilization value. On the basis of previous studies, the authors studied mineralogy, petrology, geochemistry and fluid inclusions and made water-rock reaction simulation experiments by high-pressure autoclave on Mesozoic igneous rocks in Jitai basin so as to study the effects of time, temperature and fluid composition on the water-rock reaction of igneous rocks and explore its indicative significance to the source and mechanism of lithium-potassium rich brine. The following main results were preliminarily obtained:The brine in Jitai basin is characterized by high lithium and low magnesium, indicating that the brine in Jitai basin is affected by volcanic activity; The magma in the study area was differentiated in different degrees with strong igneous alteration, which reveals that the igneous rock was greatly replaced by hydrothermal fluid and provided material source for lithium-potassium rich brine mineralization; Temperature is the main control factor of the leaching capability of fluid to elements and high-salinity fluid is the main transport carrier of ore-forming elements; The Mg/Li ratio in the brine of surface origin is mainly controlled by the original rock composition. Water-rock reaction is an important process of brine formation, and surface evaporation and concentration constitute the main mechanism of brine mineralization.