The Proterozoic volcanic rocks in South Qinling are dominated by basic volcanic rocks with SiO245%~57% and acid volcanic rocks with SiO267%~78%. The basic volcanic rocks with spilites and basalts as the major types are close to tholeiite series, whereas the acid rocks with quartz-keratophyre as the major type are close to calc-alkaline series. Both the basic and the acid volcanic rocks are enriched with REE, especially LREE, indicating that they were derived from different sources. Primitive mantle-normalized trace element patterns of the basic volcanic rocks exhibit the continental tholeiitic characteristics with highly-enriched incompatible elements and moderately-depleted Nb and Ti, suggesting that they were formed in the continental rift. According to the Sr-Nd isotopic study, the basic volcanism was closely related to the mantle plume upwelling. All the features demonstrate that the continental rift in South Qinling region was formed in Middle-Late Proterozoic, and the mantle plume activity was the precursor of the break-up of the ancient Qinling Ocean.