The invention relates to the technical field of photocatalysis, and particularly relates to a silver-phosphate-based composite visible light photocatalytic material and a preparation method thereof. The method comprises steps of: dissolving zinc oxide in water and performing ultrasonic dispersion to obtain a zinc oxide dispersion liquid; dissolving silver phosphate in deionized water, and adding the silver phosphate solution dropwise into the zinc oxide dispersion liquid under magnetic stirring to obtain a mixed solution A; adding dropwise prepared aqueous ammonia into the mixed solution A to obtain a mixed solution B; after stirring for a while, adding a phosphate solution dropwise into the mixed solution B slowly, and stirring continuously; and washing repeatedly with absolute ethanol and deionized water respectively a product after the product is subjected to suction filtration, and drying in vacuum to obtain a silver phosphate cubic/zinc oxide rod composite photocatalytic material. The material and the method are advantaged by raw materials with wide source, simple and practical preparation technology and low cost. The silver phosphate in the composite material has a regular cubic structure and regular dimensions. The material has good photocatalytic degradation effects for the organic dye rhodamine B.