Yin-deficiency-heat (YDH) syndrome is a common sub-health state of the human body in traditional Chinese medicine (TCM). However, due to the lack of objective quantitative diagnostic indicators, patients with early-stage YDH syndrome cannot be treated in time and can develop a pathological (disease) state. Therefore, it is necessary to apply modern diagnostic techniques in order to identify the biological markers for the diagnosis of early-stage YDH syndrome. In the present study, we performed Solexa sequencing and non-targeted metabolomics analysis using high-performance liquid chromatography coupled with mass spectrometry to screen differentially expressed mRNAs and differential metabolites in individuals with early-stage YDH syndrome and healthy controls. Bioinformatics methods were used to perform enrichment analysis of differentially expressed mRNAs and differential metabolites for biological functions and signaling pathways. Furthermore, we found that differentially expressed mRNAs and differential metabolites were related to energy metabolism. Real-time PCR was used to validate the mRNA expression in the serum of subjects with early-stage YDH syndrome. We found that the mitochondrially encoded NADH dehydrogenase 2 (MT-ND2) mRNA was differentially expressed in the serum of individuals with early-stage YDH syndrome. Receiver operating characteristic (ROC) curve and logistic regression analysis were used to evaluate the efficacy of the diagnostic model based on eight differential metabolites. We combined the three metabolites such as Glycine, Sphingomyelin, and Isocitrate to establish the diagnostic model with a sensitivity of 0.853 and a specificity of 0.800. The combination of the above three metabolites may serve as a potential biomarker for the diagnosis of early-stage YDH syndrome. Our study reveals potential biomarker for the diagnosis of early-stage YDH syndrome and also provides a new method for the quantification and objectification of TCM syndromes.