Abstract: Detailed observations of CL images and LA-ICP-MS detrital zircon U-Pb ages of the metasandstone samples from Liangdang area of Western Qinling provide information about the provenance of Taiyangsi Formation. The ages of detrital zircons show that the sedimentary ages of the Taiyangsi Group range from 426 to 420Ma, suggesting Ludlow to Pridoli period. The U-Pb detrital zircon ages can be assigned to four age groups: 500~420Ma, 955~550Ma, 1866~1227Ma and 3039~2132Ma. Early Paleozoic age group shows the most strong peak age of 438Ma, implying that the material source was mainly from the north margin of Western Qinling tectonic belt. The detrital zircons with Neoproterozoic age were related to the magma of the north margin of Western Qinling tectonic belt and Northern Qilian orogenic belt in the Neoproterozoic. The detrital zircons with Mesoproterozoic age and Paleoproterozoic-Neoarchaean age were mainly from the basement of Northern Qilian orogenic belt and the north margin of Western Qinling tectonic belt. A comprehensive analysis reveals that the material source of Taiyangsi Formation was mainly from the north margin of Western Qinling tectonic belt.