A systematic description and study of trace fossils that were found in Late Permian flysch factes in the region of Hezuo-Xiahe and Early to Middle Triassic flysch deposits, to the south of Lintan-Minxian are presented in this paper. Six ichnogenera, including two “facies crossing” ichnogenera (Neonereites and Scolicia) and four “deep water” ichnogenera (Cosmorhaphe, Helminthoida, Helminthopsis and Megagrapton) were found in the late Permian. Six ichnogenera were found in the Early Triassic deposits that include four “facies crossing” ichnogenera (Chondrites, Glocheria, Lennea and Palaeophycus) and two “deep water” ichnogenera (Megagrapton and Protopaleodicton), and ten were found in the Middle Triassic formations that composed of five “factes crossing” ichnogenera (Chondrites, Dictyodora, Gordia, Neonerites and Fucusopsis) and five “deep water:ichnogenera (Helminthoida, Lophoctenum.Megagrapton, Nereites and Paleodicton).The following conclusions are obtained through the comprehensive studies of the assemblages of the trace fossils:1. All of the trace fossil assemblages are of the abyssal “Nereites” ichnofacies that related to the turbidite, no pelagic sediments-related assemblages were found.2. The assemblages of trace fossils indicated that the water depths are of profundal clinoform to medium deep sea with in the limit of 2000 m.3. Tee diameters of the domichnia that developed in the Early Triassic are generally thinner than those of the Middle Triassic for the reason that the former were formed under anoxic water body with a bad circulation, while the later were formed in an open marine basin.4. The spatial distribution of the trace fossil assemblages suggested that the northern margin of North Tethys belonged to profundal clinoform during Triassic,and there was a tendency of shallowing up from the west to the east.