Heavy　metal　pollution　is　one　of　the　most　serious　environmental　problems.　Nanofiltration　(NF)　is　an　effective　and　potential　membrane　separation　technology　for　removal　of　heavy　metal　ions　from　water.　However,　the　separation　performance　and　chlorine　resistance　of　NF　membranes　should　be　further　improved　in　industry.　Herein,　to　obtain　exceptional　water　permeability　and　chlorine　resistance,　novel　positively　charged　polyamide　(PA-PDMC)　NF　membranes　were　fabricated　by　surface-initiated　atom　transfer　radical　polymerization　(SI-ATRP),　through　which　methacryloxyethyltrimethyl　ammonium　chloride　(DMC)　was　grafted　to　the　2-bromoisobutyryl　bromide　(BIBB)　exposed　on　the　surface　of　polyamide　(PA-Br1)　membrane.　The　graft　length　of　positively　charged　polymer　chains　were　controlled　by　ATRP　time,　which　furtherly　exerted　influences　on　the　surface　structures　and　properties　of　PA-PDMC　membranes.　At　the　optimal　graft　content,　the　retentions　to　MgCl2,　CaCl2,　CuCl2,　ZnCl2　of　the　as-prepared　PA-PDMC　membrane　were　92.8%,　90.8%,　93.5%　and　96.8%　respectively　with　the　flux　of　82.5　L　m(-2)　h(-1),　which　maintained　stability　during　the　long-term　operation　process　of　168　h.　Moreover,　the　PA-PDMC　membrane　exhibited　exceptional　chlorine　resistance　at　the　chlorination　condition　of　12,000　ppm　h.