Herein, an environmentally friendly and practical protocol for the visible-light-triggered regioselective radical cascade sulfonylation/cyclization of unactivated alkenes towards the synthesis of polycyclic benzimidazoles containing the sulfone group has been developed. Notably, the control experiments demonstrated that a radical pathway was involved in this reaction, and a sulfonyl radical center was initially generated via self-homolysis of sulfonyl chloride upon irradiation. Moreover, this protocol features a wide substrate scope, high atom economy, and excellent regioselectivity, and is easy to scale up.