We present a method based on surface enhanced Raman spectroscopy (SERS) to detect DNA KRAS-gene with single-base mutation. The KRAS gene belongs to the oncogenes class of genes. KRAS mutations cause normal cells to become cancerous. The detection utilizes DNA gene probes labeled by CY3 dye (as Raman marker) and plasmonic silver nanoparticles (Ag NPs) deposited on SERS substrates. SERS detect DNA via hybridization to the complementary DNA (target) sequences with single-base mutation. This SERS technique is a powerful tool and has a great potential gives both affectability and selectivity. Also, we utilized the Raman mapping to provide chemical information coupled with spatial information. The mapping image was obtained using scanning with three Raman bands over selected areas of the sample. The limit of detection (LOD) was accomplished down to a concentration 9 nM after the addition of magnesium sulfate (MgSO4) aggregated agent, causing hot spots of the aggregated Ag NPs.