The invention discloses a method for preparing nanometer bismuth tungstate by utilizing a fused salt method. According to the method, bismuth nitrate and sodium tungstate are adopted as raw materials, potassium nitrate/sodium nitrate and lithium nitrate are utilized as a fuse salt system, the raw materials are mixed and added into a molten salt system in a crucible, and the nanoscale bismuth tungstate powder is obtained through reaction. According to the method, the uniform mixing of raw material on a molecule scale can be realized, and the nanoscale bismuth tungstate powder with high purity is obtained. The method provided by the invention has the advantages that the equipment is simple, the technological process is short, the operation is simple, the product performance is excellent, and the method has an extensive application prospect.