Achieving　the　separation　of　magnesium　and　lithium　in　Salt　Lake　brine　has　become　a　huge　challenge　in　the　process　of　lithium　extraction　from　salt　lakes.　Developing　nanofiltration　membranes　with　high　magnesium　lithium　separation　performance　has　become　a　key　issue　that　needs　to　be　urgently　solved.　In　this　study,　porous　layered　double　hydroxide　(LDH)　nanosheets　were　obtained　by　chemical　etching,　which　were　then　deposited　on　the　surface　of　polyacrylonitrile　membrane　as　an　intermediate　layer.　Then,　the　positively　charged　polyamide　nanofiltration　membranes　were　prepared　on　the　surface　of　LDH　by　interfacial　polymerization　of　polyethylenimine　and　trimesoyl　chloride.　The　intermediate　layer　of　LDH　not　only　enhances　the　positive　charge　of　the　membrane　surface,　but　also　induces　the　formation　of　a　coffee　ring　structure　in　the　polyamide　layer,　improving　the　roughness　of　the　membrane　surface,　thereby　synchronously　improving　the　selectivity　and　permeability　of　the　membrane.　When　separating　a　mixture　with　a　magnesium　lithium　ratio　of　20,　the　LDH　/　polyamide　nanofiltration　membrane　has　a　magnesium　lithium　separation　factor　of　17　with　the　permeance　of　1.　15　×　10　-　4　L　/　(m2·h·Pa)　.　Moreover,　the　separation　performance　of　the　membrane　was　stable　within　100　h,　demonstrating　good　prospects　for　magnesium　lithium　separation　applications.　©　2024　Beijing　University　of　Technology.　All　rights　reserved.