Abstract: In this paper, synthesis of the diflavones(Ⅲ_a-e) from dichalcones(Ⅱ_a-e) in one step using I₂-DMSO-H₂SO₄system was reported. The dichalcones were first heated at 100℃ for about 10 min. With DMSO and a small amount of H₂SO₄, then a catalytic amount of iodine was added and the reaction mixture was further heated to give 72-100% yields of diflavones.The reaction intermediates Ⅳ_a, and Ⅳ_bwere isolated by column chromato-graphy and reaction mechanism was discussed.