Hydrogel　surface-enhanced　Raman　scattering　(SERS)　chips　with　tunable　localized　surface　plasmon　resonance　(LSPR)　wavelength　are　prepared　to　coordinate　the　chemical　enhancement　(CM)　and　electromagnetic　enhancement　(EM)　effects　for　molecules.　When　detecting　different　molecules,　a　laser　with　matched　energy　is　selected　according　to　energy　intervals　between　the　molecular　energy　levels　and　the　Fermi　level　of　Ag　nanoparticles　to　obtain　the　strongest　CM　effect.　Meanwhile,　a　hydrogel　SERS　chip　with　the　LSPR　wavelength　matching　with　the　laser　is　selected　to　gain　the　strongest　EM　effect.　As　a　result,　the　constructed　hydrogel　SERS　chips　show　outstanding　activity　to　many　molecules.　Amoxicillin,　pymetrozine,　and　chlorpyrifos　are　used　as　the　model　molecules　to　demonstrate　the　great　importance　of　CM　effect　and　the　working　principle　of　the　obtained　hydrogel　SERS　chips.　Besides　the　ultrahigh　activity,　the　obtained　hydrogel　SERS　chips　also　show　high　uniformity,　long-term　stability,　and　strong　anti-interference　to　the　sample　matrix,　and　thereby　are　highly　practical.　This　work　not　only　provides　an　efficient　strategy　for　building　high-performance　SERS　substrates,　but　also　sheds　the　light　on　the　mechanism　of　wave　selection　of　SERS.