Benzo[b]phosphole oxides are valuable and significant organic functional molecules. Therefore, extensive efforts have been dedicated to the development of an environmentally friendly and convenient synthetic strategy for benzo[b]phosphole oxides. However, several critical issues still persist in the currently available protocols. In this study, we present a direct air-oxidized strategy enabling the transformation of arylphosphine oxides into phosphinoyl radicals, which were further utilized in the synthesis of benzo[b]phosphole oxides by combining with various alkynes. In addition, the results of DFT calculations show that phosphinoyl radical formation could involve an O₂-mediated O–H bond homolysis instead of the commonly recognized P–H bond homolysis mechanism.