The gabbros were emplaced in the Dakendaban Group in the northwest of Saishiteng Mountain, west section of the tectonic belt of northern margin of Qaidam Basin. They are characterized by low SiO₂, high Al₂O₃, rich MgO and FeO^T but poor ALK, thus belonging to subalkalic calc-alkaline series. Meanwhile, The rocks are enriched in LILE and depleted in HFSE. The chondrite-normalized REE patterns show right-inclined shape with LREE enrichment and flat HREE. The rocks are characterized by low Zr and Zr/Y ratio. The authors consider that the gabbros emplaced in the Saishiteng Mountain were formed in the island-arc environment of an active continental margin. LA-ICP-MS zircon U-Pb dating of gabbros yielded the formation time of 271±3 Ma. Comprehensive analysis shows that the original rocks of gabbros can be considered as a product of partial melting of spinel lherzolite in the lithospheric mantle, and the magma might have undergone fractional crystallization of strong clinopyroxene and weak plagioclase during its evolution, which however was slightly assimilated and contaminated by mid-upper crust materials in the emplacement process. In combination with the tectonic evolution of the tectonic belt of northern margin of Qaidam Basin and the geochronological and geochemical characteristics of contemporary intrusive rocks, it is concluded that the gabbros were produced in the process when the southward subduction of Zongwulong oceanic crust toward Oulongbuluke block in early Middle Permian. The authors hold that the subduction-collision event of the western part of Zongwulong structural belt was obviously earlier than that of its eastern segment, and the difference of the subduction-collision time shows that the Zongwulong Ocean were probably characterized by scissor-like closure early in the west and late in the east.