Recently,　Mn4+　activated　red　double　perovskite　red　phosphors　have　gained　great　attention　due　to　their　particular　luminescent　properties.　In　this　study,　a　novel　far-red　phosphor　Ba2LaTaO6:　Mn4+　was　successfully　prepared　by　solid-state　reaction.　The　crystal　structure　and　bandgap　structure　were　analyzed　using　X-Ray　Diffraction　(XRD)　Rietveld　refinement　and　density　functional　theory　(DFT)　calculations.　The　photoluminescent　performance　of　Ba2LaTaO6:　Mn4+　was　investigated　to　evaluate　its　availability　in　plant　growth　LED　and　temperature　sensing.　The　results　indicate　that　Ba2LaTaO6:　Mn4+　can　match　ultraviolet　chips　and　emit　a　narrow-band　far-red　light　centering　at　690　nm.　The　emission　band　of　the　fabricated　LED　matches　well　with　the　absorption　bands　of　chlorophyll-a　and　b.　In　addition,　Ba2LaTaO6:　Mn(4+　)has　a　high　temperature　sensitive　(3.2%　K-1　@　450　K),　which　is　of　great　value　in　thermal　sensing.　The　luminescent　mechanism　was　dissected　in-depth　based　on　configurational-coordinate　model,　crystal-field　and　Racah　parameters.　It　is　expected　that　the　research　of　Ba2LaTaO6:　Mn4+　offers　insight　into　developing　new　functional　materials.