In this research, a series of BiOCl-Ag/AgBr_x (BAA_x) heterojunctions with surface plasmon resonance (SPR) effect of metallic Ag were synthesized by a facile one-pot solvothermal method. For the superior photosensitive effect of AgBr co-catalyst, all BAA_x samples exhibited much enhanced response to visible light. For the formation of BiOCl-AgBr heterojunction and existence of metallic Ag plasma, the BAA_x photocatalysts exhibited very superior interfacial charge migration, and the recombination of photoexcited electron-hole pairs could be effectively controlled. Research showed that the BAA_0.04 heterojunction exhibited the highest photocatalytic activity under visible light irradiation, and various pollutants in water system could be decomposed effectively. Furthermore, the BAA_0.04 heterojunction possessed very robust photostability, its crystal structure and photocatalytic activity almost remained unchanged after being used several times.