Antibacterial poly(3-allyl-5,5-dimethylhydantoin-co-vinylamine) (P(ADMH-co-VAm)) N-halamine precursor with amine functional group was synthesized,and it was used to improve the thin film composite polyamide (PA) reverse osmosis (RO) membrane antibacterial and chlorine resistance properties through second interfacial polymerization process.The modification procedure is easy,which can be incorporated into the large scale manufacturing conveniently.The resultant membrane shares similar permselectivity with some commonly used RO membranes,higher than the virgin membrane,as shown in Fig.1 (a);meanwhile,it demonstrates significantly improved anti-biofouling and chlorine resistance properties,as shown in Fig.1 (b).The P(ADMH-co-VAm) plays as sacrificial layer when membrane suffers from chlorine attack,keep the selective PA sub-layer intact.Upon chlorination,P(ADMH-co-VAm) transfers into N-halamine antibacterial polymer,which endows the membrane with potent antibacterial property.After killing bacteria,the N-halamine returns to precursor.Thus the membrane demonstrating regeneration ability.The regeneration properties of the chlorine resistance and anti-biofouling performances were characterized through cycling experiments.