The efficiency and stability of plasmonic photocatalysts that closely related with microstructure characteristics are intensively studied for practical applications. Here, a plasmonic photocatalyst Ag/AgNbO3 was successfully synthesized by a facile combustion method, and systematically characterized by XRD, XPS, DRS, SEM, TEM and photocurrent techniques. The photocatalytic activity of Ag/AgNbO3 as a function of Ag vs Nb contents are assessed toward Rhodamine B (RhB) and tetracycline (TC) degradation under the visible-light. At an optimal Ag content, the greatest photocatalytic efficiency of as-prepared Ag/AgNbO3 on photodegradation of RhB (0.0447 min(-1)) was 2 times higher than that of currently reported solvents routes (0.0213 min(-1)). Meanwhile, the experimental and theoretical studies were conducted to examine the photocatalytic efficiency and stability of the as-prepared photocatalysts, the results show that the photocatalytic efficiency and stability are related with the SPR effect, ferroelectric polarization, specific exposed crystal-facets and interfacial crystallinity. This work may also provide new ideas for the design and preparation of other highly efficient and stable plasmonic photocatalysts.