Organic phosphorus compounds containing sp³-C—P(O) bonds are increasingly widely applied in catalysis, pharmaceuticals, materials, pesticides, and other fields, and their synthesis has become a research hotspot in chemistry. Diarylmethyl phosphine oxides are important organic phosphorus compounds containing sp³-C—P(O) bonds, but their synthesis is limited. Traditional methods for their synthesis require the use of halogenated compounds and harsh reaction conditions. A new method for the copper-mediated synthesis of (diarylmethyl)diarylphosphine oxides has been developed. This method involves the cleavage of the sp³-C—N bond in N-diarylmethylsulfonamides, leading to the formation of diarylmethyl carbocations. The carbocations then react with diarylphosphine oxides to construct sp³-C—P(O) bonds. Our method only requires the addition of stoichiometric, inexpensive CuBr₂ and produces a series of target compounds in satisfactory yields. Thus, it provides a convenient, and cost-effective pathway for the synthesis of diarylmethyl phosphine oxides.