Surface-enhanced　Raman　spectroscopy　(SERS)　provides　a　rapid　and　nondestructive　method　for　biological　plasma　analysis,　offering　unparalleled　sensitivity　and　specificity.　However,　most　current　studies　predominantly　employ　the　drop-cast　method,　where　liquid　samples　are　dried　on　the　SERS　substrate　for　spectral　recording.　While　effective,　this　method　is　both　time-consuming　and　inconsistent.　Additionally,　the　Raman　spectral　signal　of　uric　acid　in　plasma　often　dominates,　overshadowing　other　crucial　biomarkers　necessary　for　disease　differentiation.　In　this　study,　we　present　the　application　of　label-free　SERS　detection　for　distinguishing　early　stage　lung　cancer　(LC)　from　healthy　controls　(HC)　using　plasma　samples.　Plasma　was　diluted,　adjusted　to　a　weakly　acidic　pH,　and　combined　with　silver　nanoparticles　(Ag　NPs)　for　SERS　analysis.　To　maintain　the　plasma　in　a　liquid　state　and　prevent　evaporation,　liquid　paraffin　was　employed.　Our　findings　indicate　that　a　10-fold　dilution　of　plasma　under　weakly　acidic　conditions　significantly　enhanced　diagnostic　performance,　achieving　an　area　under　the　receiver　operating　characteristic　curve　(AUC)　of　0.975.　This　method　is　featured　by　its　simplicity　and　high　efficiency,　presenting　a　promising　strategy　for　the　minimally　invasive　diagnosis　of　early　stage　LC　using　SERS　technology.