Heavy metal pollution is one of the most serious environmental problems. Nanofiltration is an effective and potential membrane separation technology for removal of heavy metal ions from water. However, the separation performance and chlorine resistance of the nanofiltration membrane should be further improved in industry. In this study, positively charged polyamide (PA-PDMC) nanofiltration membranes were fabricated to remove heavy metal ions from water. The obtained membrane had high flux and chlorine resistance by grafting methacryloxyethyltrimethyl ammonium chloride (DMC) on the surface of 2-bromoisobutyryl bromide (BIBB) immobilized polyamide (PA-Br1) membranes via surface-initiated atom transfer radical polymerization (SI-ATRP). The retentions to divalent cations of the as-prepared PA-PDMC membrane was above 90% with the flux of 82.5 L m-2 h-1. Furthermore, the PA-PDMC membrane showed a stable separation performance during a long-time filtration process of 168 h, which exhibited an exceptional chlorine resistance.