The U-Pb ages of single zircon grains contained in the sandstone samples were analyzed by the LA-ICP-MS method, the sediment provenances and geological significance were discussed. The results show that: ① The detrital zircon age of the tuffaceous sandstone from the Upper Ordovician Pingliang Formation can be obviously divided into three groups, the first group is Early Paleozoic which ranges from 407~477Ma, the peak value is 454Ma, accounting for about 72.5% of the total dates. The second group is Meso—Neoproterozoic which ranges from 588~1548Ma, the peak value is 962Ma, accounting for about 22.5% of the total dates. The last group is Paleoproterozoic which ranges from 1612~2496Ma, accounting for about 5% of the total dates.② The group of 407~477Ma indicates that its material provenances may mainly come from the North Qinling—Qilian island arc complex belt in adjacent regions. The group between 588~1548Ma and 1612~2496Ma indicates that its material provenances were mainly from the North Qinling orogenic belt and the Qilian orogenic belt, with the little of material from the basement of North China block. ③ A comprehensive analysis shows that the material provenances of Pingliang Formation were much more complicated and characterized by obvious diversity and complexity. The indication is that sedimentary environment is the limits of residual marginal sea basin between North Qinling—Qilian island arc complex belt and the southwest of Ordos block in the Pingliang age Ordovician.