In　recent　years,　lanthanide-doped　upconversion　nanocrystals　have　been　developed　as　a　new　class　of　fluorescent　probe　that　have　become　promising　alternatives　to　organic　fluorophores　and　quantum　dots　for　applications　in　biological　and　medical　fields.　This　technique　offers　large　anti-Stokes　shifts,　low　autofluorescence　background,　sharp　emission　bandwidths,　high　photochemical　stability,　and　deep　penetration　depth.　According　to　the　recently　reports,　NaLuF4　is　a　better　host　material　for　lanthanide　upconversion　compared　to　the　classic　NaYF4　host.　Some　reviews　concerning　the　upconversion　nanocrystals　have　been　reported,　but　no　one　focuses　on　the　NaLuF4-based　nanocrystals.　In　this　review,　recent　reports　regarding　the　synthesis　of　NaLuF4-based　nanocrystals　and　their　upconversion　luminescence　properties,　surface　modification,　and　biological　applications　are　summarized.