A　series　of　LnNi　heterometallic　coordination　polymers,　{[Ln2Ni(MIDA)4(H2O)6](H2O)4}　(Ln　=　La　(1),　Ce　(2),　Pr　(3),　and　Nd　(4);　H2MIDA　=　N-methyl-iminodiacetic　acid),　were　obtained　under　hydrothermal　conditions.　Single　crystal　X-ray　diffraction　revealed　that　they　feature　two-dimensional　isomorphic　frameworks,　which　could　be　viewed　as　the　construction　by　one-dimensional　{Ln}n　chain　connecting　by　bridges　of　[Ni(MIDA)2]2.　The　magnetic　measurements　reveal　that　compounds　24　exhibit　antiferromagnetic　properties.　TGA　results　indicate　compounds　1　and　4　have　good　thermostability　with　the　critical　temperature　of　375　degrees　C.