A silver phosphate (Ag 3 PO 4 )/silver (Ag)/silver halide (AgX, X = Cl, Br, or I) ternary composite photocatalysts were prepared by loading Ag nanoparticles on Ag 3 PO 4 tetrapods followed with in situ halogenation. The interface charge transfer behavior in the Ag 3 PO 4 /Ag/AgX nanocomposite was studied, and the photocatalytic performance was also evaluated. The results show that the Ag 3 PO 4 /Ag/AgI photocatalyst exhibits higher photocatalytic activity than the other two photocatalysts due to the more matched band structure between AgI and Ag 3 PO 4 . An internal electric field (IEF) from Ag 3 PO 4 to AgI is formed at the heterogeneous interface, so the photogenerated electrons at the conduction band of AgI can rapidly transfer to the valence band of Ag 3 PO 4 and recombine with photogenerated holes, which is consistent with the S-scheme charge transfer mechanism. Meanwhile, the photogenerated electrons left at the conduction band of Ag 3 PO 4 can transfer to Ag nanoparticles due to the Schottky junction and react with oxygen to produce • O 2 − , which is proved to be the main active species in the photocatalytic procedure. This tandem junction modulated between the S-scheme heterojunction and Schottky junction promotes the efficient separation of photogenerated carriers, thus significantly increasing the average PL lifetime of electrons by 2.95 times. Therefore, the Ag 3 PO 4 /Ag/AgI photocatalyst exhibits excellent photocatalytic activity for the degradation of methylene blue and norfloxacin. The seven consecutive cyclic tests prove the good stability of the photocatalyst, thus showing the application potential in the field of sewage treatment.