A novel 3D structure Ag/p-Ag2S/n-BiVO4 plasmonic p-n heterojunction photocatalyst was successfully fabricated via a depositing p-type Ag2S on n-type BiVO4, followed by light reduction. In this innovative plasmonic p-n heterojunction photocatalyst strcture, p-n heterojunction can play the role of suppression of charge recombination, and surface plasmon resonance of Ag can enhance the absorption of visible light confirmed by finite difference time domain (FDTD) simulations method. For the photocatalytic oxidation of oxytetracycline hydrochloride (OTH) and reduction of Cr6+, the Ag/p-Ag2S/n-BiVO(4)exhibits excellent photocatalytic performance, compared with BiVO4 and p-Ag2S/n-BiVO4. The results of active species detection reveal that h(+) radical is the main reactive species in the photocatalytic oxidation of OTH. Moreover, 13 photocatalytic degradation intermediates and products of OTH were also identified by the gas chromatography-mass spectrometer (GC-MS). Finally, the photocatalytic oxidation and reduction mechanism over Ag/p-Ag2S/n-BiVO4 was discussed in detail. The present study will benefit the development of the new plasmonic p-n heterojunction photocatalysts and would be of great importance to meet ever-increasing environmental demands in the future.