The extremely thick Triassic flysh sedimentary cover around the Songpan- Ganzi orogeny makes it difficult to assess its basement properties, subduction- collision process and magmatism history. Therefore, widely exposed numerous granitoid plutons and minor mafic plutons have become important research objects to understand the mystery of the tectonic evolution of the Songpan- Ganzi orogeny. Zircon U- Pb dating results show that the Dawu granodiorite was formed at 223. 5~217. 4 Ma, the Luhuo monzonite crystallization age is 219. 4 Ma, and the age of gabbro is 218. 9 Ma, all belonging to the products of Late Triassic magmatism. The chemical composition demonstrates that the granitoid rocks are I- type granitoids, in which the Luhuo monzonites have high Ba and Sr contents, relatively high; uniform εHf(t) value (-3. 69~-1. 65) indicated that they are most likely formed by partial melting of the enriched juvenile crustal sources. The Dawu granodiorites have dispersed εHf(t) value (-13. 51~0. 41); their field and geochemical characteristics indicate that they were formed by the mixing of mantle derived melt and ancient crust derived melt. The Luhuo gabbros are relatively enriched in large ion lithophile elements (Rb, Ba, Sr) and radioactive element U, but depleted in high strength elements (Nb, Ta, Ti), which are similar to those of island arc basalt, derived from the partial melting of mantle wedge metasomatized by flow/melt. Based on the information in the region, we propose a new understanding of the evolution history of the Ganzi- Litang Ocean and believe that it was not subducted to the south, but also has a history of north subduction. The Late Triassic Dawu- Luhuo magmatites were formed by the subduction of the Ganzi- Litang Ocean to the north under the Songpan- Ganzi block.