Abstract: There are lesser research on when the Late Paleozoic rift belt of the Beishan area began to rift. A complete volcanic edifice is identified in the southern Beishan rift belt through 1∶50 000 regional geological survey. The rock association is composed of andesite, dacite, basalt, rhyolite and pyroclastic rocks with the zircon U-Pb age ranging between 313～300 Ma.The volcanic rocks are characterized with high NaO₂ and Mg^#, low CaO and TiO₂, belonging to calc-alkaline series. The REE pattern is distributed in obvious right-tendency with little depletion of Eu (δEu=0.72～1.00), enriched in large ion lithophile elements Rb, Th, K and LREE, and depleted in Nb, Ta, P and Ti. Based on the geochemical characteristics of rocks and key indices such as (Th/Nb)_N and (Nb/La)_N, it indicates that the volcanic rocks were intensely mixed with crust materials during the magma eruption. The sedimentary sequence in clastic rocks infers that it should be formed in an intra-continental environment. Diagrams of Zr/Nb-Nb/Th and Zr/Y-Nb/Y show that the basic volcanic rocks may derived from the tectonic environment associated with mantle plumes. Based on the diagram of Zr/Y-Zr and Th/Hf-Ta/Hf, in combination with the regional geological characteristics, the authors consider that the volcanic rocks might occur in the initial cracking environment of continental rift. This is the earliest age-information of the rift zone reported so far, which indicates that the southern Beishan area has initially entered in the intracontinental initial rift environment in the Late Carboniferous.