The Indosinian granites in South China are mainly distributed in Hunan, Jiangxi, Guangxi Provinces and their adjacent areas. The large scale of these granites makes them an important research objective in granite petrology of South China. However, there are still questions on their tectonic implication and their relationship with mineralization. Methods: This paper takes the Ziyunshan granitic complex in Shuangfeng County, western Hunan Province, and the Shibanwan granitic complex in Ziyuan County, northeastern Guangxi Zhuang Autonomous Region, as investigated samples, and carries out petrographic, geochemical and zirconological researches on their main intrusive phases and subsequent intrusive phases. Results and Conclusions: (1) The main intrusive phases of the two granitic complexes are a granodiorite for the Ziyunshan complex and a biotite monzogranite for the Shibanwan complex. They show whole- rock compositions of normal granite（e. g., 67. 23%~71. 94% SiO2 and 2. 03%~3. 73% FeOT）, and are enriched in compatible trace elements（e. g., Ba, Sr, Zr, etc.）, with negative Eu anomalies（average Eu/Eu* ratio is 0. 49）. Their zircon U- Pb ages and εHf(t) values are 239. 6±2. 3 Ma and -4. 9~-1. 0 for the Ziyunshan granodiorite, and 239. 7±3. 3 Ma and -8. 8~-1. 1 for the Shibanwan biotite monzogranite, respectively. Therefore, this paper concludes that they belong to the early Indosinian syn- orogenic granites. (2) The subsequent intrusive phases of the two granitic complexes are a muscovite alkali- feldspar granite for the Ziyunshan complex and a two- mica alkali- feldspar granite for the Shibanwan complex, with high SiO2 content (73. 92%~76. 55%), low FeOT content（0. 71%~1. 21%）, enriched in compatible trace elements（e. g. Rb, Ta, U, etc.）, with strong negative Eu anomalies（average Eu/Eu* ratio is 0. 14）；Their zircon U- Pb ages and εHf(t) values are 217. 4±2. 8 Ma and -7. 3~-1. 3 for the Ziyunshan muscovite alkali- feldspar granite, and 217. 4±2. 2 Ma and -10. 3~-3. 1 for the Shibanwan two- mica alkali- feldspar granite, respectively. Therefore, this paper concludes that they belong to the late Indosinian post- orogenic granites. (3) In addition, the U- Pb ages and εHf(t) values of the hydrothermal zircons from the Yuntoujie W deposit in the Shibanwan granitic complex are 217. 7±2. 8 Ma and -10. 5~-3. 7, respectively, which are completely similar to the U- Pb ages and Hf isotopic compositions of the hydrothermal zircons from the Shibanwan two- mica alkali- feldspar granite, indicating a direct genetic relationship between the two. This paper proposes that the South China plate was compressed by three plates in the Early Triassic, including the Indosinian plate, the North China plate and the Pacific plate, resulting in anatexis of crustal thickening. At ~239 Ma, the compression in this area reached its peak, and the initial granitic magma in the deep- seated magma chamber emplaced in the forceful mechanisms to form syn- orogenic granites（i. e., the main intrusive phases of the granitic complexes）；after the compression peak, huge amount of granitic magma in deep- seated chamber underwent an ultra- long time of fractional crystallization, resulting in occurrence of residual magma extremely enriched in ore- forming material at the top of magma chamber；At ~225 Ma, the tectonic environment of this area changed from compression to extension, and reached the extension peak at ~217 Ma, when very small volume of highly- fractionated residual magma ascended rapidly along these crustal extensional faults from the deep- seated magma chamber in the permissive mechanisms；Due to the abrupt decrease of pressure and temperature, the highly- fractionated residual magma during the emplacement could split into two portions by fluid—melt immiscibility: ore- forming material- bearing silicious fluid and strongly felsic melt；the former formed the quartz vein- type or greisen- type magmatic—hydrothermal deposits, while the latter formed the post- orogenic granites（i. e., the subsequent intrusive phases of the granitic complexes）. (4) Based on the peak period of compression（~239 Ma）determined by the ages of the syn- orogenic granites, and the peak period of extension（~217 Ma）determined by the ages of the post- orogenic granites in this area, as well as a large amount of geochronological data of diagenesis and mineralization, this study suggests that the time frame of the Indosinian movement in Hunan, Jiangxi, Guangxi Province and their adjacent areas could be divided into two periods: the early Indosinian（250~225 Ma）in the compression environment and the late Indosinian（225~215 Ma）in the extension environment, and that the majority of magmatic—hydrothermal deposits should be formed during the peak of the late Indosinian extension（~217 Ma）.