Display omitted Functionalized graphene oxide is a novel type of highly efficient biosensing material. In this study, we present a carboxyl-functionalized graphene oxide (GO-COOH)-based surface plasmon resonance (SPR) chip for the rapid and quantitative detection of non-small cell lung carcinoma (NSCLC) via the cytolerayin 19 (CK19) protein biomarker in spiked human plasma. We demonstrated the binding specificity of kinetic analysis of interactions between GO-COOH and anti-CK19 and CK19 protein. We also calculated the relationship between the SPR angle and refractive index of GO-COOH, and demonstrated that COOH modified GO sheets on Au film can enhance the field energy propagation intensity of an SPR sensor, resulting in a higher sensitivity for the detection of CK19 protein compared to a conventional Au-based SPR chip. The immunosensor was constructed and engineered by immobilizing a low concentration (10 μg/mL) of CK19 antibody on an SPR chip. The lowest detectable concentration was as low as 1 fg/mL. A spiked 10% human plasma CK19 detection limit of 0.05 pg/mL was achieved, well below the normal physiological level of serum protein (3.3 ng/mL). Therefore, a carboxyl-GO based SPR biosensor appears to have high sensitivity and specificity for the detection of clinical whole plasma biomarkers and possible application in diagnosing diseases.