Enhancing membrane flux, rejection, antimicrobial and chlorine resistance has been the focus of reverse osmosis membrane research. The permselectivity, chlorine resistance and antimicrobial properties of a polyamide (PA) membrane were improved by immobilization of self-synthesized amine functional hydantoin derivative poly(3-allyl-5,5-dimethylhydantoin-co-vinylamine) (P(ADMH-co-VAm)). The chlorine resistance and antimicrobial property of the modified membrane could be regenerated due to the reversible transition between hydantoin and N-halamine. The lab-scale virgin and modified membranes were systematically characterized, and their performances were evaluated and compared with some representative commercial membranes. The modified membrane showed similar permselectivity, but higher and regenerable chlorine resistance and antimicrobial property as compared with the commercial membrane e.g., BW30FR. Next, a pilot-scale 0.4-m wide continuous membrane production process was performed to fabricate membrane element. The permselectivity of the modified element was also improved. During the six "chlorination-sterilization" operation cycles, the element exhibited high antimicrobial property with small permselectivity changes. Thus, both the lab-scale and pilot-scale testing results demonstrated the improved performances of the modified membrane.