The Awengco- Yanhu complex pluton is located in the northern margin of the Shiquanhe- Namco ophiolite mélange zone. It is an important archive of magma response during the subduction, collision and orogeny of the Shiquanhe- Namco Tethys ocean. Research on the complex pluton is of great significance for understanding the evolution of the Tethys ocean basin on the Qinghai- Tibet Plateau. In this paper, a systematic study of geology, geochemistry and zircon U- Pb geochronology has been carried out in the Awengco- Yanhu complex pluton. The spatial- temporal distribution of the complex pluton is summarized, and the genetic type, source characteristics and tectonic background of the complex pluton are discussed. The complex pluton is mainly composed of quartz diorite, monzodiorite, granodiorite, syenite granite and monzogranite. It is a set of island arc magmatic rock assemblage. Its diagenetic age is 120~104 Ma, belonging to the end of Early Cretaceous, and its spatial distribution has a trend from south to North, and from early to late. The geochemical characteristics of the rocks show that from quartz diorite to monzogranite, there is a trend of evolution from calc alkaline series to shoshonite series. The main body belongs to quasi- aluminous to weakly peraluminous I- type granite, with high fractionation degree of light rare earth elements. However, there is no obvious differentiation of heavy rare earth elements, a weak negative Eu anomaly, enrichment of Rb, K and other large ion lithophile elements, Ta, Zr, HF and other high field strength elements. Light rare earth elements are relatively depleted in high field strength elements such as Nb, P, Ti and heavy rare earth elements, which are characterized by island arc magmatic rocks. Based on the results of this study, combined with the existing regional data, it is considered that the Awengco- Yanhu complex pluton was formed in the background of northward subduction of the Shiquanhe- Namco Tethys ocean basin. The fluid rising from the subducted plate resulted in the partial melting of the overlying mantle wedge material and the formation of mantle derived magma. Under the effect of density difference, the mantle derived magma migrated upward and underintruded into the new generation. During the end of Early Cretaceous (104. 8±1. 4 Ma), the Shiquanhe- Namco Tethys Oceanic crust continued to subduct northward, and the molasse formation in the Jingzhushan Formation in the early Late Cretaceous meant that the ocean basin was completely closed.