Herein, Ag nanoparticles (AgNPs) were loaded on oxidized porous g-C3N4 (PCNO) via photo-assisted reduction method. Compared with PCNO, Ag/PCNO plasmonic photocatalysts possessed remarkably enhanced photocatalytic performances in both pollutant degradation and disinfection under visible light irradiation. The optimum photocatalytic activity of Ag/PCNO at a loading amount of 2.0 wt% (Ag-2/PCNO) on amaranth degradation was almost 2.4 times as fast as that of PCNO. Additionally, Ag-2/PCNO could inactivate about 99.4% of Staphylococcus aureus (S. aureus) cells after 3 h of irradiation, whereas only about 29.6% of S. aureus cells were inactivated by PCNO. The enhancement of photocatalytic activities for Ag/PCNO composites could be ascribed to the combination of the SPR effect of AgNPs and the synergistic effect from PCNO molecules, which resulted in enhanced absorption in visible-light region, improved charge transfer, and reduced charge recombination. Moreover, h(+) and center dot O-2(-) were the dominate reactive species for Ag/PCNO composites to remove azo pigments and pathogenic bacteria efficiently during the photocatalytic process.