The adsorbability of the dicationic Langmuir-Blodgett (LB) films of N,N’-omega-p-xylylenebis(stearyldimethylammonium chloride) (XSAC) with octadecane was investigated by using methyl orange (MO) as an adsorbate. As a result, high adsorbability due to ionic interaction was observed for MO molecules. The structural characterizations of XSAC LB films before and after MO adsorption were also carried out by applying spectroscopic methods. It was found that MO molecules have the same molecular arrangements in both MO-adsorbed XSAC LB films and XSAC-MO complexed LB films and that the bilayer in the LB films took an interdigitated structure.