In the Lower Proterozoic, there had existed strongly plate subduction in the westem margin of the Yangtze Plate. When the paleo Qinghai-Tibet oceanic plate subducting northeastern forward, the basaltic-andesite volcanics of Ailaoshan Group and Dibadu Formation were formed due to the collision with the Paleo-Yangtze Plate. The trace elements geochendstry study shows that tectonic settings of these two groups are continental-margin-arc and back-arc-basin in subduction belt respectively. Consequently the Lower Proterozoic subduction system in the westem marin of the Yangne Plate has been established. Ailaoshan Group is actually westem boundary of the Yangtze Plate, which and Dibadu Formation both composed the Lower Proterozoic metalnorphic basement of westem mpin in the Yangtze Plate. Their origin was enriched mantle that was coednated by crustal sedhents taken by subducted slab In the Lower Proterozoic, there had been strongly plate subduction in the westem margin of the Yangtze Plate. When the paleo Qinghai-Tibet oceanic plate subducting northeastern forward, the basaltic-andesite volcanics of Ailaoshan Group and Dibadu Formation were due due to the collision with the Paleo-Yangtze Plate. The trace elements geochendstry study shows that tectonic settings of these two groups are continental-margin-arc and back-arc-basin in subduction belt respectively. has been established. Ailaoshan Group is actually westem boundary of the Yangtze Plate, which and Dibadu Formation both composed the Lower Proterozoic metalnorphic basement of westem mpin in the Yangtze Plate. Their origin was enriched mantle that was coednated by crustal sedhents taken by subducted slab