In　this　study,　four　kinds　of　upconversion　nanocrystals　(UCNs)　have　been　successfully　synthesized　by　a　facile　solvothernnal　method.　The　morphology,　crystalline　phase,　composition,　grain　size,　upconversion　luminescence　and　cell　image　of　the　UCNs　were　investigated.　The　properties　of　the　NaLuF4-based　UCNs　were　compared　with　the　counterparts　of　NaYF4-based　UCNs.　It　is　found　that　the　NaLuF4-based　UCNs　are　apt　to　form　hexagonal　phase　structures,　while　NaYF4-based　UCNs　of　NaYF4:Yb,　Er　and　NaYF4:Gd,　Yb,　Er　are　cubic　and　hexagonal　phases　respectively.　The　upconversion　emission　intensities　of　the　NaLuF4-based　UCNs　are　higher　than　that　of　NaYF4-based　UCNs,　and　Gd3+　presented　UCNs　are　higher　than　that　of　Gd3+　absented　UCNs.　The　bioimaging　application　of　NaLuF4:Gd,　Yb,　Er　shows　that　bright　upconversion　luminescence　can　be　observed　when　UCNs-labeled　He　La　cells　are　excited　with　980　nm　light.