Removal of E. coli from water by modified polypropylene (PP) nonwoven cloths which were prepared through radiation-induced grafting of 4-vinyl pyridine (4-VP) onto PP nonwoven cloths and followed by quaterization was carried out by filtration. The results showed that the content and structure of the pyridinium group on PP nonwoven cloths were important factors to affect their antibacterial activity. The antibacterial activity increased with the number of piled sheets of the used nonwoven cloths and decreased with increase of the viable bacterial cell concentrations in the influent and with filtration rates. The activity detection results found that modified PP nonwoven cloths possessed the ability to capture the bacterial cell alive, and no morphological changes of adhered bacterial cells were observed using SEM; thus, the surfaces of the modified PP nonwoven cloths may not be bactericidal, but bacteriostatic.