Diphenylphosphoric acid is an important pharmaceutical and pesticide intermediate. At present, the reported preparation method is benzene and phosphorus trichloride with benzene as solvent, aluminum chloride as fu acid agent to make phenylphosphorus dichloride, phenylphosphorus dichloride with aluminum chloride as catalyst for disproportionation reaction to make dichemicalbook phenylphosphorus chloride, diphenylphosphorus chloride oxidized to diphenylphosphoryl chloride by oxygen under cryogenic cooling, and then hydrolyzed to diphenylphosphoric acid. However, the existing diphenylphosphoric acid synthesis process is polluting, has high requirements for equipment performance, and the total yield is only 30%, and the cost is high.