As　an　important　water　resource,　brackish　water　has　been　extensively　utilized　in　the　industry.　However,　there　are　few　cases　of　municipal　potable　water　treatment　plants　that　use　low　chloride　content　brackish　water　as　the　source.　In　this　paper,　the　brackish　water　treatment　efficiency　of　ultrafiltration　(UF)/nanofiltration　(NF)　dual-membrane　process　was　evaluated　in　a　municipal　potable　water　treatment　plant,　combining　with　a　pilot　optimization　experiment.　Results　showed　that　UF　guaranteed　the　inlet　water　quality　of　NF　and　NF　could　efficiently　reject　organics　and　salts,　with　a　chloride　removal　over　95　%.　Pilot　experiment　showed　that　the　UF　membrane　flux　decreased　only　12　%　after　continuously　30-days　operation　under　the　optimized　UF　operation　conditions,　effectively　extending　the　chemical　cleaning　interval.　Response　surface　method　was　adopted　in　the　NF　removal　efficiency　and　energy　consumption　optimization.　With　the　increase　of　feed　water　conductivity,　the　influences　of　pressure　and　recovery　on　the　removal　efficiency　were　strengthened,　and　the　removal　efficiency　could　be　regulated　over　a　wider　range.　When　the　conductivity　was　less　than　3500　μS/cm,　NF　could　perform　high　treatment　efficiency　under　the　operation　pressure　of　0.65−0.85　MPa　and　recovery　of　55–70　%.　Besides,　as　feed　conductivity　increased,　it　was　necessary　to　increase　the　pressure　and　reduce　the　recovery　within　this　range　to　maintain　efficient　operation.　This　paper　will　provide　a　guidance　for　the　UF/NF　dual-membrane　process　design　and　operational　optimization.　©　2020　Elsevier　Ltd