Objective: To investigate the relationship between chemical indexes of exfoliated cells of tongue coating and TCM syndromes and pathological stages in patients with middle or advanced primary bronchial lung cancer and to provide objective basis for TCM syndrome differentiation. Methods: Chemical indexes of SDH, LDH, Mercapto (-SH) and acid phosphatase (ACP) of tongue coating cells were measured in 152 patients with advanced lung cancer. According to the TCM standard, 152 patients were divided into four types of syndromes, which are qi deficiency and phlegm dampness, qi and blood stagnation,yin deficiency and heat toxicity,and deficiency of qi and yin. Results: The pale red tongue with white thin coating was mostly found in the normal group, which accounts for 82.22 %. The pale fat tongue with white and greasy coating was mostly found in the syndrome of qi deficiency and phlegm dampness, which accounts for 84.85 %. The red tongue with little coating was mostly seen in patients with the syndrome of yin deficiency and heat toxicity, which accounts for 69.77 %. The pale fat tongue with teeth marks and thin coating was mostly found in the syndrome of deficiency of both qi and yin, which accounts for 82.93 %; The purple and dark tongue was mostly found in patients with the syndrome of qi and blood stasis, which accounts for 88.57 %. Syndrome of Qi deficiency and phlegm dampness was mostly found in the lung squamous carcinoma group, which accounts for 35.09 %. Syndrome of yin deficiency and heat toxicity was mostly found in the lung adenocarcinoma group, which accounts for 58.14 %. Syndrome of Qi and blood stagnation was mostly found in the large or small cell lung cancer group, which accounts for 57.89.09 %. Syndrome with deficiency of both qi and yin was mostly found in the alveolar carcinoma group, which accounts for 67.65 %. Content of -SH and activities of LDH, SDH in the qi-yin deficiency group was lower than that in the healthy control group(P<0.01), and activity of ACP in the qi-deficiency and phlegm-dampness group were significantly lowered (P<0.01). The content of -SH in the adenocarcinoma group was significantly higher than that in the normal group, and the activities of LDH, SDH and ACP were significantly higher than that in the normal group (P<0.01). The activities of LDH, SDH and ACP in the large and small cell carcinoma groups were significantly decreased compared with those in normal group (P<0.01). The -SH content in the squamous cell carcinoma group was mostly decreased and lower than that in the normal group. Conclusion: The chemical indexes of tongue coating exfoliated cells could be used to distinguish different TCM syndromes of middle and advanced lung cancer, which could be served as the objective basis for tongue diagnosis in TCM.