Fluorescent　and　magnetic　bi-functional　NaLuF4-based　upconversion　nanocrystals　have　been　developed　by　a　facile　thermal　decomposition　method.　The　influences　of　Mn2+　and　Gd3+　doping　on　the　upconversion　luminescent　and　magnetic　properties　of　the　nanocrystals　were　investigated.　The　results　show　that　Mn2+　doping　can　promote　the　transition　of　green　to　red　and　increase　the　red　emission　significantly.　When　the　Mn2+　and　Gd3+　are　co-doped　in　the　nanocrystals,　it　has　a　synergistic　effect　which　can　further　improve　the　transition　and　red　emission.　Moreover,　the　nanocrystals　co-doped　with　Mn2+　and　Gd3+　exhibit　excellent　superparamagnetic　properties.　These　results　suggest　that　the　developed　nanocrystals,　which　have　strong　pure　red　upconversion　emission　and　superparamagnetic　properties,　can　serve　as　a　potential　upconversion　luminescence　and　magnetic　resonance　probe　for　dual-modality　bioimaging.　This　work　presents　a　facile　and　effective　method　for　modulating　the　transition　of　short-wavelength　emission　to　red　emission　of　upconversion　nanocrystals,　leading　the　naocrystals　exhibiting　excellent　upconversion　luminescence　and　magnetic　properties.