The Lancang group, an important part of the Tethys orogenic belt, is located in the Changning- Menglian combined belt in the Sanjiang area of western Yunnan, China. In this paper, we have conducted zircon U- Pb dating, Hf isotope analyses and petrogeochemistry of albite- leptite to determine the genesis, chronology, and geotectonic evolution of the rocks in the Shuangjiang area. The detrital zircons with strongly oscillatory zoning employed for dating are of magmatic origin from albite- leptite. The U- Pb date, weighted average of 206Pb/238U, is 476. 5±1. 6 Ma, which is Early Ordovician (O1). The εHf(t) from the in- situ analysis of Hf isotopes is -5. 6～-2. 2 and the TDMc Age is 1591～1802 Ma indicating that the materials in the source area were formed by partial melting of ancient crustal materials from the terminal Early- Proterozoic to the early Middle- Proterozoic. According to petrogeochemical analysis, the original rock of albite- leptite is granitic diorite which is a peraluminous S- type granite with high SiO2=67. 89%～68. 91%, aluminum- rich Al2O3=14. 48%～15. 14% and high potassium calc- alkaline. The characteristics i. e. enrichment in LREE, the overall tilt to “right”, δEu（0. 60～0. 64）and strong negative Eu, indicated that plagioclase has separated from the magma. The analysis shows that the original rock of albite- leptite is island- arc granite, which formed in the continent- arc collision stage around Changning- Menglian Tethys, has the same tectonic background as the volcanic rocks of the Huimin Formation in the Ordovician. As Tethys entered intracontinental subduction- grinding stage, the island- arc granite is a subduction accretionary complex, between the Changning- Menglian combined belts and the Lincang Batholith, forming tectonic sheet of the Lancang group.