-The　development　of　sensitive　analytical　methods　is　of　prime　importance　for　the　detection　of　pesticide　residues　on　the　surfaces　of　fruits　and　vegetables　at　extremely　low　concentrations.　Here,　we　synthesized　Ag-decorated　three-dimensional　ZnO　nanoflowers　(ZnO@Ag)　composed　of　ultrathin　nanosheets　as　surface　-enhanced　Raman　spectroscopy　(SERS)　substrates.　Combined　with　the　finite　-difference　time　-domain　(FDTD)　method,　it　is　proven　that　the　ultrathin　nanosheets　greatly　improve　the　electromagnetic　coupling　between　the　two　metal　nanoparticles　due　to　the　high　refractive　index　of　ZnO　and　generate　new　＂hot　spots＂.　The　nanosheets　also　endow　the　incident　light　with　multiple　reflections　to　motivate　the　local　electromagnetic　field.　The　substrate　presents　high　sensitivity　and　the　enhancement　factor　was　as　high　as　2.98　x　107　utilizing　R6G　as　probe　molecules.　The　detection　concentration　of　thiram　and　malachite　green　(MG)　solutions　can　reach　10-10　M　and　10-9　M,　respectively.　For　the　real　-life　sample　assays,　the　substrate　can　simultaneously　detect　the　two　pesticides　on　apple　skin　with　high　sensitivity.　The　research　also　reveals　the　importance　of　semiconductors　toward　the　local　electromagnetic　field　enhancement　in　noble　metal　-semiconductor　substrates,　benefiting　the　realization　of　highly　sensitive　SERS　substrates　and　the　wide　application　of　the　SERS　technology　in　real　-world　scenarios.