We investigate the surface Plasmon resonances (SPRs) behavior of silver niobate (AgNbO3) experimentally.Result shows that the localized surface Plasmon resonances (LSPRs) of AgNbO3 combining with its interband transitions enlarge the absorption band across the whole UV-Visible light range.It possesses huge potential in high performance light-harvest device application.The ab initio density functional theory (DFT) calculations are carried out to obtain the further insight of the SPRs behaviors.Theoretical study indicates that the SPRs effect of AgNbO3 is due to the weakly bound Ag atoms in the perovskite structure.