Coumarins are a key class of heterocyclic lactone compounds, which have good biological activity. 3?sulfonyl coumarin derivatives were prepared by visible light promoted reaction of benzoalkynyl esters with sodium benzenesulfonate, and their reaction mechanism was studied. The results showed that under mild reaction conditions, 3?sulfonyl coumarin derivatives can be synthesized with moderate to good yields using sodium benzenesulfite as the precursor of sulfonyl radicals and persulfate as the oxidant through a cascade radical addition cyclization strategy, providing a concise, green, and efficient synthetic route for the preparation of functionalized coumarin derivatives.