Objective:To describe the characteristic of tongue images of patients with lung cancer of different Chinese medicine(CM) syndromes and to reveal the elemental rule on the changes of the tongue images. Methods:A total of 207 patients with lung cancer were divided into four syndrome groups according to the theory of CM:Fei(肺) and Shen(肾) deficiency syndrome(Group A,72 cases),Pi(脾) deficiency and phlegm dampness syndrome(Group B,57 cases),phlegm-heat retention in Fei(Group C,36 cases) and yin asthenia generating intrinsic heat syndrome(Group D,42 cases).The tongue parameters were detected by tongue image digital analysis instrument,and the tongue images were described with qualitative,tongue color and quantitative analysis,respectively.The International Commission on Illumination(CIE) L~*a~*b~*(CIELAB) color model was used for the quantitative classification.Results:There was a significant statistical difference between different syndrome groups of lung cancer on tongue color,coating color,and thickness of tongue coating(P<0.01),and there was significant statistical difference between the four syndrome groups on Lab values of the tongue and coating(P<0.05).The correct identification rate of discriminant function on the raw data was 65.7%,including 72.2%for Group C,69.4%for Group A,69.0%for Group D and 54.4%for Group B.Conclusions:A tongue image digital analysis instrument can objectively describe the tongue features of patients with different syndromes of lung cancer.The tongue diagnosis is very important to syndrome differentiation in CM.Tongue diagnosis should be combined with some important characteristics of syndromes in the future to establish a“combination of four examination methods,including inspection,auscultation,interrogation,and pulse-feeling and palpation”in the tongue diagnostic system. Objective: To describe the characteristic of tongue images of patients with lung cancer of different Chinese medicine (CM) syndromes and to reveal the elemental rule on the changes of the tongue images. Methods: A total of 207 patients with lung cancer were divided into four syndrome groups according to the theory of CM: Fei and Shen deficiency syndrome (Group A, 72 cases), Pi deficiency and phlegm dampness syndrome (Group B, 57 cases), phlegm-heat retention in Fei (Group C, 36 cases) and yin asthenia generating intrinsic heat syndrome (Group D, 42 cases). The tongue parameters were detected by tongue image digital analysis instrument, and the tongue images were described with qualitative, tongue color and quantitative analysis, respectively. The International Commission on Illumination (CIE) L ~ * a ~ * b ~ * (CIELAB) color model was used for the quantitative classification. Results: There was a significant statistical difference between different syndrome groups of lung cancer on tongue color, coatin (P <0.01), and there was significant statistical difference between the four syndrome groups on Lab values ​​of the tongue and coating (P <0.05). The correct identification rate of discriminant function on the raw data was 65.7%, including 72.2% for Group C, 69.4% for Group A, 69.0% for Group D and 54.4% for Group B. Conclusions: A tongue image digital analysis instrument can objectively describe the tongue features of patients with different syndromes of lung cancer. The tongue diagnosis is very important to syndrome differentiation in CM. Tongue diagnosis should be combined with some important characteristics of syndromes in the future to establish a “combination of four examination methods, including inspection, auscultation, interrogation, and pulse-feeling and palpation ”in the tongue diagnostic system.