An attempt was made to synthesize an adsorbent by the photo-induced grafting of acrylic acid(AA) onto polypropylene nonwoven using benzophenone(BP) as a photosensitizer in an $CH_{3}OH-H_{2}O$ medium. As BP concentration was increased, the gragt yield was increased up to a specific value and then decreased, and the effect of AA concentation showed the same tendency. it was also found that the graft yield increased with reaction time and reaction temperature. The amount of ammonia gas absorbed by AA grafted polypropylene(PP-g-AA) nonwoven was dependent on the graft yield, adsorption time and ammonia gas pressure. The adsorption capacity of ammonia gas by the PP-g-AA nonwoven with graft yield of 11.6% was 5.68 mmole/g, which is much higher than that of active carbon or silica gel.