Abstract: The Yunnan-Guizhou-Guangxi Rift System is located on the western margin of the Yangtze Plate and its rifting activities initiated at the time of Devonian and ended at the Triassic Period. In the rift system,the sedimentary volcanic rocks over 10000 m have been developed with bimodal rift volcanic rocks,sedimentary sequences of rift type,carbonate sedimentary rocks characterized by platform sedimentation,and pelitic and siliceous sediments characterized by sedimentary differentiation of trough-basin. During the early and middle stages of the rift evolution,the clastic sediments were derived from the east and west sides of the rift shoulders and were migrated southward after they accumulated at the rift axis while the clastic sediments were sourced from its southern and southeastern areas and migrated towards north and northwest during the late stage of the rift evolution. Therefore, this rift opens towards south and can be named as a rifted-trough.