Noble　metal　surface　plasmon　resonance　or　photonic　crystals　(PCs)　effect　is　a　novel　and　effective　method　for　improving　upconversion　luminescence　(UCL).　UCL　can　be　effected　by　the　size,　thickness　of　the　noble　metal　film　and　the　photonic　band　gap　(PBG)　of　the　PCs.　So　it　is　important　to　improve　UCL　by　coupling　surface　plasmons　resonance　(SPR)　with　PCs　effect.　In　this　work,　the　PCs/Ag/UC　composite　films　were　fabricated　to　improve　the　upconversion　emission　of　NaGdF4:Er3+/Yb3+/Al3+　nanocrystals,　and　the　influence　of　the　Ag　layer　thickness　on　spectral　properties　was　investigated.　Studies　reveal　that　the　Ag　layer　thickness　and　morphology　have　a　major　impact　on　the　Ag　nanoparticles　(NPs)　plasma　resonance　and　UCL　intensity　of　NaGdF4:Er3+/Yb3+/Al3+　nanocrystals　for　PCs/Ag/UC　composite　films.　The　highest　enhancement　factors　of　the　red　and　green　emissions　were　found　to　be　43　and　42　under　980 nm　excitation,　respectively.　That　is　attributed　to　the　coupling　effect　of　the　Ag　NPs　local　SPR　and　PCs　Bragg　reflection,　the　local　electromagnetic　field　enhancement　produced　by　the　excitation　wavelength　overlapping　with　the　photonic　band　gap　and　strong　plasmon　resonance　band　overlapping　with　emission　wavelength.　©　2022,　The　Author(s),　under　exclusive　licence　to　Springer-Verlag　GmbH,　DE　part　of　Springer　Nature.