The Mesoproterozoic—Neoproterozoic volcanic rock series of the Bikou G ro up is di stributed along the northern margin of the Yangtze plate and the southern margin of the Q inling orogenic belt, occurring in a continental rift tensional environment a n d has the nature of continental rift volcanic rocks with the following three cha racteristics: ① the volcanic rocks are of bimodal assemblages and consist of b asi c volcanic rocks (spilite or spilitic tuff) and acid volcanic rocks (quartzker a tophyre or quartzkeratophyric tuff); ② two magma series can be identified in the basic volcanic rocks, namely the alkali basalt magma series and thetholeiit ic magma s eries; ③ the volcanic rocks are rich in LREE and LIL. United studies on trace e lements and isotope (including SmNd and RbSr) indicate that the basic volcan ic rocks are derived from the mantle plume source similar to the OIB source and th e acid volcanic rocks are the remelted product of the crust. The distribution of Mesoproterozoic—N eoproterozoic continental volcanic series of the Bikou and Xixiang Groups on the northern margin of the Yangtze plate suggests that continental rift tension a l volcanism is developed in the Mesoproterozoic—Neoproterozoic,which is the maj or accretion period of the Qinling crust.