Lung cancer has the highest mortality rate because of the difficulty in early diagnosis. Surface enhanced Raman spectroscopy (SERS) can detect the bio-fluids at a molecular level, thus is capable of predicting lung cancer at an early stage. In this paper, we used SERS on saliva to detect its components for the diagnosis of lung cancer. Principal component analysis combined with linear discriminant analysis was used for testing the diagnosing accuracy. We got a total accuracy of 82%. This experiment shows the possibility of using SERS of saliva as a means for lung cancer diagnosis.