The flavonoids as inhibitors of CYP1Al exhibit chemopreventive effects against certain procarcinogens and have been considered as the promising cancer preventive agents.A series of novel 7,8-dimethoxy-αnaphthoflavones as the substrate analogs were designed and prepared.The enzyme assay suggested that all of these new flavones were stronger inhibitors of CYP1 Al than the lead compoundα-naphthoflavone. Among the tested ones,3h showed the most potent inhibitory effects. The flavonoids as inhibitors of CYP1Al exhibit chemopreventive effects against certain procarcinogens and have been considered as the promising cancer preventive agents. A series of novel 7,8-dimethoxy-αnaphthoflavones as the substrate analogs were designed and prepared.The enzyme assay suggested that all of These new flavones were stronger inhibitors of CYP1 Al than the lead compound α-naphthoflavone. Among the tested ones, 3h showed the most potent inhibitory effects.