Abstract: The Western Pacific subduction zone is one of the most typical and active ones in the world, featuring a vast distribution of trench-island arc-back-arc basin systems. The Mariana subduction zone is a typical ocean-ocean subduction zone, and the Mariana Trough is an important component tectonic unit and an ideal area to elucidate the subduction without the influence of continental crust materials. The magmatic processes of the Mariana Trough were studied in detail, such as rock mantle source properties, subduction components, and magmatic evolution. The research clarified that: (1) the magma source in the Mariana Trough is mostly depleted mantle as it features peridotite dominance and the degree of partial melting of the source mantle varies in different regions. (2) The subduction components from altered oceanic crust and sediments in different parts are affected to different degrees of mantle melting and initial magma composition in different regions. (3) The influence of subduction components gradually increased from the middle section to the north and south sections. The middle section was mainly affected by melt from sediments, and the south and north sections were more significantly affected by hydrous fluids. (4) During the magma evolution in different regions or even in the same region, the fractional crystallization of olivine, pyroxene, and plagioclase can well explain the diverse rock types and different phenocryst assemblages in basaltic rocks. The achievements above could promote the understanding of the magmatism process in the Mariana Trough and also strengthen the deep understanding of tectonic-magmatism in the subduction zone.