In this work, we developed a phosphine-catalyzed cascade lactonization/[2 + 1] annulation reaction between vinyl oxiranes and sulfonium compounds for the highly diastereoselective construction of spiro-2(3H)-furanone skeletons. The cascade cycloaddition proceeds via the 2(5H)-furanone phosphonium intermediate, introducing an oxygen-containing active intermediate for phosphine catalysis. These findings highlight the significant potential of harnessing vinyl oxiranes as versatile synthons for constructing spirocyclic compounds through simultaneous multicyclic skeleton formation.