Abstract: OBJECTIVE To explore the serum metabolomic mechanism of the common tongue coatings (TCs) in the patients with gastric cancer. METHODS The gastric cancer patients (n=101) were divided into four groups: white thin TC group (n=42)， white thick TC group (n=9)， yellow thin TC group (n=28) and yellow thick TC group (n=22). Twenty-two healthy volunteers with white thin TC were recruited as controls. GC-MS was used to detect the serum metabolomic. Multi-factors analysis methods were conducted to screen the metabolic markers of the common TCs in gastric cancer patients， and enrichment analysis was carried out to predict the metabolic pathways. RESULTS Compared with the control group， the white thin TC of gastric cancer patients occupied 13 special metabolic molecules involved in 31 metabolic pathways， the white thick TC of gastric cancer patients held 15 special metabolic molecules involved in 26 metabolic pathways， the yellow thin TC of gastric cancer patients held 9 special metabolic molecules involved in 15 metabolic pathways， and the yellow thick TC of gastric cancer patients had 8 metabolic molecules involved in 12 metabolic pathways. The level of 4-aminobutyric acid elevated in all the gastric cancer patients were observed involving with tyrosine metabolic pathway. CONCLUSION Different TCs reflect characteristic serum metabolomic machanism in gastric cancer patients.