Objectives: Bangong Lake-Nujiang River Suture Zone is one of the main suture zones in Qinghai-Xizang(Tibet) Plateau, and researches of it have great significance on the researches of the evolutional process of the Tethyan ocean and orogenic belt. Methods:This paper, for the first time, investigates the causes, tectonic settings, and instructions on regional tectonic evolution of volcanic rock by using bulk geochemistry analysis based on systematic field geological investigation of the Shamuluo Formation volcanic rocks in Anglonggangri area located in the west section of the Bangong Lake-Nujiang River Suture Zone. Results: Three volcanic eruption cycles are divided from the top to the bottom with the lithology of andesite and andesitic volcanoclastic rock. Geochemical analysis shows that volcanic rocks in these three cycles belong to calc-alkaline series featured by island arc volcanic rock with relative enrichment of LREE and incompatible element and relative depletion of HREE and high field strength elements like Nb, P, and Ti. Volcanic rocks in the first cycle are featured by classical high-Mg andesite, which implies that plate subduction is likely to start. Tectonic setting from the first eruption cycle to the third one is a transition to continental marginal arc from oceanic island arc. Volcanic rocks in Anglonggangri area are formed during oceanic plate subduction from oceanic crust to the blow of it, and the initial time of subduction is no later than late Jurassic. Source region is depleted-weak enriched mantle influenced by fluid metasomatism of subduction slab. Mantle magma is formed during the partial melting of overriding mantle wedge resulted from ascending fluid of subduction slab, and it migrates upwards as a result of density difference, then intrudes into the lower crust and triggers the partial melting of mantle wedge in the lower crust. Moreover, mantle magma blends with those in the lower crust, thus mother magma of andesite in Anglonggangri area comes into being. Magma source may be contaminated with crustal materials during its ascent process. In addition, magmatic evolution is dominated by partial melting process. Conclusions: Combined with regional tectonic setting, it is considered that the formation of the Shamuluo volcanic rocks is closely correlated with northward subduction of Bangong Lake-Nujiang River’s Tethyan oceanic crust beneath the Qiangtang blocks, and the Shamuluo Formation rests with angular unconformity on the Muggar Kangri Group-complex in the area cannot be the evidence for the close of Tethys ocean of Bangong Lake-Nujiang River Suture Zone.