A removal of radioactive contaminant using smectite suspension, has been studied. Specimens contaminated with ¹³⁷Cs solution in one hand, and dust/ ¹³⁷Cs solution in the other hand were used to evaluate the decontamination performance of the smectite suspensions as a decontamination agent. Used specimens for this study were weight-concrete of research reactor(HANARO) construction material, fire brick, red brick, silicate brick, and wood. The results of this study show that smectite suspension technology was effective to decontaminate of an urban surface materials.