The disintegration of the strata within the CentralQiangtang accretionary complex (CQAC) provides important role in determining the temporalspatial evolution of the Longmu CoShuanghu suture and the PaleoTethys Ocean. For a long time, however，the study of the Triassic strata in this area remains poor, particularly in lacking a correlation with the existing knowledge about the Triassic oceancontinent subduction/collision tectonics. Three outcrops on the north of Lanling were found to host one set of a MiddleLate Triassic platformfacies carbonatite intercalated with finegrained clastic rocks and silicalite. They occur as brittle faultbounded blocks and are superimposed on the Middle Permian ophiolitic mélange, with an approximately horizontal and uninverted bedding, but its top and bottom are tectonically removed away. Based on the lithological assemblages, thickness variation of limestone layers and fossil distribution, three sedimentary subfacies were determined: restricted platform, open platform and shoal in the platform margin. The shoal facies bioclastic/intraclast limestones contain abundant hexacoralia fossils consisting of six genera including one species such as Conophyllia sp.，Omphalopyllia sp.，Coryphyllia sp.，Pamirastraea sp.，Margarophyllia cf. capitata，and Craspedophyllia sp.，which suggest an age of Ladinian of Middle TriassicNorian of Late Triassic. A comparative analysis on the MiddleUpper Triassic strata of the Qiangtang basin shows different sedimentation systems occurring in North Qiangtan terrane, central accretionary complex (CQAC), and South Qiangtan terrane. Both structural relationship and stratigraphic characteristics indicate that the newly discovered MiddleUpper Triassic carbonatite characterizes a portion of the forearc deposition in the active continental margin in south of North Qiangtang terrane, that is, slope basin immediately above the Triassic accretion wedge，which therefore implies a northward subduction polarity for the PaleoTethys Ocean. On the basis of tectonic background of the MiddleUpper Triassic in Central Qiangtang and time of the fossil assemblages, the closure of the PaleoTethys ocean was hence speculated to happen in middle Norian of Late Triassic.