Polyhedral bismuth vanadate (BVO) material was prepared using a straightforward hydrothermal method, and then a small-sized AgNi bimetallic co-catalyst was synthesized in situ on the surface of the polyhedral BVO through a chemical reduction method. The photocatalytic performance of the catalyst was studied. The physicochemical properties of the prepared AgNi/BVO material were characterized through various techniques, including X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL) spectroscopy, and nitrogen adsorption-desorption analysis. The results indicated that AgNi bimetallic co-catalysts were extensively loaded onto the unique morphology of BVO polyhedra, significantly increasing the metal attachment sites. Simultaneously, the AgNi loading also improved the crystallinity of BVO. The silver surface plasmon resonance effect, in conjunction with the nickel's lattice interface effect, enhanced the BVO catalyst's absorption of visible light and improved the separation of photo-generated electrons, thereby increasing the photocatalytic activity. Photocatalytic degradation experiments using MB (methylene blue) as a model pollutant demonstrated that when the ratio was 3:1, AgNi/BVO exhibited the highest catalytic activity, with a reaction rate of 5.4 times higher than that of BVO under visible light irradiation. This photocatalyst retained excellent photocatalytic activity even after four cycles of use.