Of various types of geothermal systems, magma chamber- heated geothermal systems are of great scientific significance and high exploitation value. Magmatic fluids released from a magma chamber serving as the heat source of a geothermal system are rich in strongly acidic gases, and therefore are capable of altering reservoir hostrocks substantially, which is the fundamental reason why hydrogeochemical processes occurring in a magmatic geothermal system is quite different from those in a non- magmatic geothermal system. In general, three types of geothermal waters are expected to occur in a geothermal area with either a shallow or a deep magmatic heat source, ie. acidic SO 4, SO 4- Cl, or Cl- SO 4 waters, neutral Cl- Na or Cl- HCO 3- Na waters, and weakly alkaline HCO 3- Cl- Na or HCO 3- Na waters. Correspondingly, concurrence of these three geothermal waters turns out to be a useful hydrogeochemical criterion to judge if a hydrothermal system hosted by non- carbonate rocks is being heated by magma chambers. In China, magmatic geothermal systems are basically distributed in the southern Tibet- western Yunnan geothermal belt and the Taiwan geothermal belt. The magma chambers below the high- temperature hydrothermal systems in southern Tibet were formed probably due to the partial melting of Tibetan crust induced by crustal thickening, or resulted from the occurrence of a near E- W trending mantle wedge during the northward subduction of the Indian continental lithosphere and its further upwelling.