Upconversion　nanocrystals　have　many　advantages　over　other　fluorescent　materials.　However,　their　upconversion　luminescence　intensities　are　not　desirable,　limiting　their　applications　for　highly　sensitive　detection.　Therefore,　it　is　really　important　to　enhance　upconversion　luminescent　intensities　of　upconversion　nanocrystals.　In　the　present　study,　a　novel　Ag　core　and　upconversion　nanocrystal　shell　based　nanocomposite　Ag@SiO2@Lu2O3:Gd/Yb/Er　for　metal-enhanced　upconversion　luminescence　was　fabricated　successfully,　and　its　morphology,　crystalline　phase,　composition,　optical　property,　and　cell　imaging　application　were　investigated.　It　was　found　that　a　maximum　upconversion　luminescence　enhancement　of　30-fold　was　obtained　in　comparison　with　the　control　without　a　silver　core,　and　the　nanocomposite　exhibited　bright　upconversion　luminescence　when　it　was　used　for　imaging　with　He　La　cells.　This　enhancement　potentially　increases　the　overall　upconversion　nanocrystal　detectability,　endowing　the　nanocomposite　with　a　potential　capability　for　highly　sensitive　biological,　medical,　and　optical　detection.