The　demand　to　improve　the　chlorine　resistance　of　polyamide　(PA)　membranes　is　escalated　with　greater　amounts　of　chlorine-containing　disinfectant　being　used　in　global　water　treatment　during　the　COVID-19　pandemic.　In　this　work,　we　designed　thiophene-functionalized　poly(ethyleneimine)　(TPEI)　materials　first　and　grafted　them　onto　a　conventional　PA　membrane　to　develop　novel　nanofiltration　membranes　(PEI-M,　TPEI-1-M,　TPEI-2-M).　These　membranes　have　dual-functionalized　selective　surfaces　covered　by　hydrophilic　amino　groups　and　electron-rich　thiophene　moieties,　which　endow　these　membranes　with　superior　chlorine　resistance　and　improved　separation　performance.　The　modified　membranes　increase　the　rejection　of　MgCl2　from　86.5%　of　the　nascent　PA　membrane　(PA-M)　to　higher　than　93.0%　without　sacrificing　the　membrane　water　permeability.　More　stable　separation　performance　is　achieved　with　all　of　the　as-prepared　membranes　than　PA-M　after　exposure　to　a　2000　ppm　sodium　hypochlorite　solution.　TPEI-2-M　outperforms　other　membranes　after　being　treated　in　a　chlorination　intensity　of　16,000　ppm　center　dot　h　with　the　smallest　flux　loss　and　the　highest　MgCl2　rejection.　This　is　mainly　ascribed　to　the　highest　amount　of　amino　and　thiophene　moieties　on　the　TPEI-2-M　surface.　This　study　provides　an　effective　protocol　for　developing　novel　PA-based　nanofiltration　membranes　while　demonstrating　its　superiority　over　current　technologies　with　exceptional　separation　performance　and　antichlorine　ability.