Two-dimensional　(2D)　nanofluidics　technology　has　shown　great　potential　in　efficient　osmotic　energy　harvesting,　but　the　lack　of　anion-selective　2D　nanofluidic　membranes　limits　the　development　of　full　concentration　cells　towards　real-world　applications.　Herein,　an　anion-selective　2D　nanofluidic　membrane　(2D-NFM)　was　constructed　based　on　hydrotalcite-like　layered　double-hydroxides　(LDHs),　whose　naturally　positively　charged　surface　and　nanoconfined　interlamellar　channels　endowed　the　membrane　with　excellent　anion　selectivity　in　a　wide　range　of　electrolyte　concentration.　The　selective　anion　transport　was　further　confirmed　by　the　lower　calculated　transmission　barrier　of　anions　compared　with　the　cations　based　on　the　strong　electrostatic　interaction　within　the　positively　charged　nanochannels.　Benefiting　from　good　hydrophilicity　and　narrow　nanochannels,　the　output　power　density　of　the　2D-NFM　in　an　NaCl　solution　with　a　50-fold　concentration　gradient　could　reach　3.06　W　m-2,　while　the　value　could　reach　3.92　W　m-2　when　natural　seawater　and　river　water　were　used　as　electrolytes.　This　work　is　expected　to　provide　an　effective　strategy　for　constructing　high-performance　anion-selective　2D　nanofluidic　devices　for　osmotic　energy　harvesting.