The Baijianshan granodiorite, located in the eastern segment of the HongliugouLapeiquan ophiolite belt in North Altyn Tagh, occurs as large stocks intruding into the Lapeiquan Group. The wholerock geochemical analysis shows that the granodiorite is low in SiO2(62.58%~65.05%), high in CaO(4.02%~4.98%), characterized with (A/CNK)<1.0(0.89~0.98), enriched in K, Rb and Ba, depleted in Nb, Ta, Zr and Ti, suggesting it belongs to weakly peraluminous calcalkaline series and be characteristic of I type granite. The total REE content of the Baijianshan granodiorite varies from 90.2 to 137.8 ug/g. The chondritenormalized REE distribution patterns show relative enrichment of LREE with weakly negative Eu anomaly (δEuN=0.84~0.92). There is a large range of εHf(t) from -2.96 to 7.99, which is interpreted to be influenced by magmatic contamination. The geological characteristics and the experimental petrology data jointly show that the granodiorite was formed by partial melting of lower crust rocks and contaminated by the upper crust materals. Zircon LA-ICP-MS dating of granodiorite yields a UPb age of 475.2±2.0 Ma for zircons characterized by oscillatory zoning and Th/U>0.3, and hence this age can be regarded as the formation age of the granodiorite. Combined with regional geological background, the Baijianshan granodiorite should be an eastern component of early Paleozoic magamatic activity in the HongliugouLapeiquan ophiolite belt, which, together with the Qiashikansayi granodiorite and the Bashikaogong quartzdiorite (from the western Hongliugou area) forms a common islandarc magmatic rock belt. The early Paleozoic subductiontype granitoids, distributed in both northern and southern sides of EWtrending HongliugouLapeiquan ophiolite belt, also shows that the whole North Altyn ocean is characterized by bidirectional subduction.