Objectives: In the southeastern Beishan orogenic belt，there occurs a complex metamorphic sequence at Wutongjing area,which were taken as Ordovician-Silurian strata. Controversies exist on its formation ages and regional stratigraphic correlation,which greatly limits the understanding of regional geological evolution of the region.Methods: To determine the age of the sequence,LA-ICP-MS zircon U-Pb dating was performed on hornblende epidote biotite plagioclase gneiss and muscovite quartz schist of Formation Complex c of the sequence and monzonitic granite vein that intruded the gneiss in this area.Results: Weighted mean 206Pb/238U zircon ages of 419.8 ± 2.7 Ma,421.5 ± 0.8 Ma and 417.0 ± 3.4 Ma were obtained,respectively.Obviously the age of the vein constrains the lower limit of the sequence.Conclusion: Therefore,we suggest that the formation age of the Formation Complex c of the Ordovician-Silurian sequence was ca.420 Ma,i.e.,late Silurian.In combination of two zircon U-Pb single-peak ages of 427 Ma and 428 Ma of the Formation Complex b of the sequence (Song Dongfang et al.,2016),we conclude that the sequence formed in Silurian,and the previous Ordovician-Silurian sequence were in fact deposited as Silurian strata.Both rock formations and geochemistry demonstrate that the sequence originally formed in the fore-arc basin associated with subduction of the early Paleozoic Paleo-Asian Ocean to the Dunhuang Massif to the south.