The invention discloses alpha bismuth oxide/bismuth vanadate and a preparation method thereof. The preparation method provided by the invention comprises the following steps that firstly adding bismuth nitrate into nitric acid; adding ammonium metavanadate into a sodium hydroxide solution; mixing the two solutions for regulating and controlling the pH values; then, performing drying, grinding androasting to obtain bismuth vanadate; mixing the obtained bismuth vanadate powder with the bismuth oxychloride powder; performing dispersion; then, adding a sodium hydroxide solution; performing stirring, washing and drying; then, obtaining the alpha bismuth oxide/bismuth vanadate powder. The sodium hydroxide is used for performing in-situ conversion on the bismuth oxychloride to obtain the alpha bismuth oxide in the alpha bismuth oxide/bismuth vanadate. The method has the advantages that the proportioning ratio between two phases of ingredients can be easily regulated and controlled; the production cost is low; the process method is simple and convenient, and the like.