There occur Cenozoic continental acid volcanic rocks in Tianshui area, West Qinling Mountains. They are composed mainly of rhyolite and partly of rhyolitic breccia tuffaceous lava as well as rhyolitic ignimbrite (breccia) tuff, together with a small amount of breccia tuff and volcanic breccia. Thesevolcanic rocks are geochemically characterized by Si-, alkali-enrichment and Al-, Ca-depletion and belong to nonorogenic alkaline rocks, similar to continentalrift type alkaline rhyolite. New evidence shows that Cenozoic acid volcanic rocks were formed by partial melting of crustal rocks in a continental extension setting, related to sinistral strike-slip shearing of Weihe faulted zone in early Cenozoic.