A direct α-Csp3-H methylenation of arylketones to form C═C bond using dimethyl sulfoxide as one-carbon source is achieved under transition metal-free reaction condition. Various aryl ketone derivatives react readily with DMSO, producing the α,β-unsaturated carbonyl compounds in yields of 42 to 90%. This method features a transition metal-free reaction condition, wide substrate scope and using DMSO as novel one-carbon source to form C═C bond, thus providing an efficient and expeditious approach to an important class of α,β-unsaturated carbonyl compounds. Based on the preliminary experiments, a plausible mechanism of this transformation is disclosed.