The adsorbents for toxic gas were prepared by radiation induced grafting of styrene onto polypropylene fabrics and its sulfornation. The adsorption characteristics of ammonia gas by the adsorbents modified with sulfonic acid was examined. The maximum grafting yield was obtained at 60 vol% styrene at 70 ℃ for 15 hrs. The degree of grafting(%) was enhanced with acides. The contents of -SO3H group ranged from 0.5 to 1.8 mmol/g with chlorosulfonic acids in dichloroethane. The adsorption reactor for ammonia gas in the air was examined. The adsorption capacity of ammonia gas by polyproylene fabrics-grafted syrene having 8.3mmol/g was much higher than of actived carbon or silica gel.