In this work, plasmonic Ag nanoparticles (NPs) decorated BiOCOOH microflowers as one kind of efficient visible-light-driven photocatalysts were prepared via a one-pot solvothermal method and systematically characterized. Compared with pristine BiOCOOH, Ag/BiOCOOH heterojunctions showed greatly enhanced visible light photocatalytic activities towards RhB degradation. Especially, the 5wt% Ag/BiOCOOH heterojunction displayed the maximum activity, and the degradation rate is 10.9 times higher than that obtained by using pristine BiOCOOH. The exceptional photocatalytic activity of Ag/BiOCOOH is attributed to the surface plasmon resonance (SPR) effect induced by Ag NPs and formation of the heterojunction between Ag and BiOCOOH. Holes and superoxide radicals mainly dominate the RhB degradation. More importantly, Ag/BiOCOOH is highly stable in photocatalysis.