Urban surface decontamination properties using smectite-hectorite decontamination agent containing ammonium ion, have been studied. Contaminated specimens with dust/ ＾137Cs and 137＾Cs solution were used to evaluate the decontamination performance of the agent. The results of this study show that the decontamination agent was effective to ionic and particulate contaminants due to high adhesion force and ion exchange capability.