The Early Paleozoic granite in Nanpingxueshan in the eastern part of the Tianshuihai terrane, West Kunlun, consists of mediumgrained porphyritic biotitequartz monzonite (485Ma) and medium to finegrained biotitequartz monzonite (528Ma). Chemically, the two rocks are enriched in Si and alkali, and depleted in TFe2O3, MgO and CaO, thus suggesting that they can be grouped into highK calcalkaline and weakly peraluminous granitoids. In terms of trace elements and rare earth elements, the two granites are enriched in Rb, Th, U, K, Pb and LREE, depleted in Ba, Sr, Nb, Ta, Ti and P, with high Rb/Sr, Rb/Ba, Nb/Ta, Y/Yb ratios and strongly negative europium anomalies. They also have lower Zr, Nb, Ce and Y concentrations relative to that of the typical Atype granites. Integrated geological and geochemical discrimination suggests that the Nanpingxueshan granite should be genetically ascribed to highly fractionated Itype granites. The mediumgrained porphyritic biotitequartz monzonite and medium to fine grained biotitequartz monzonite have narrow zircon Hf isotopic compositions, with positive εHf (t) values ranging from 0.9 ~ 5.3 and 1.4 ~ 5.6, respectively. Correspondingly, they have Mesoproterozoic twostage Hf model ages ranging from 1118 ~ 1398Ma and 1136 ~ 1396Ma, respectively. Similar geochemical features and zircon Hf isotopic compositions indicate that they were the products of the same magma evolution. Based on evolution history of the regional structure, we can speculate the ProtoTethys may be bidirectional subduction during early Mesozoic. The Nanpingxueshan granite was formed through a certain extent of fractional crystallization and at least two partial melting of the Mesoproterozoic young crust, which was induced by uprising of mantle magma and invaded into lower crust during the continuous southward subductioncollision of Tethys ocean during Early Cambrian to Early Ordovician.