Objective: β-catenin is closely associated with proliferation, differentiation, invasion and metastasis of tumor cells.C-myc is proved to be abnormally expressed in various kinds of malignant neoplasmas. This study is aimed to investigate the features of β-catenin and C-myc expressions in thymoma and the corresponding clinical significance. Method:Immunochemistry was used to detect the features of expressions of β-catenin and C-myc in thymoma and normal thymus. Of the 105 samples, according to Beratz classification, there were: epithelial type 34; lymphocyte type 35; mixed type 31 and shuttle cell type 5. According to Masaoka classification, there were: stage 1: 38; stage 2: 32; stage 3:20 and stage 4: 15.According to WHO classification, there were: type A 20; type AB 19; type B1 21; type B2 17; type B3 13 and type C 15.Results: Different ways of expression was revealed in different stages of thymomas. With the progress of thymoma, the expression of β-catenin on cell membrane decreased, while increased in cytoplasma and nucleus, even with nucleus shift. The expression of C-myc increased in invasive thymoma. Abnormal expression of β-catenin and C-myc increased, with significant difference(P＜0.05). Conclusion: The different ways of expression and diversity of expression level may indicate the biological characters of thymoma, and could be used as an objective index for invasive thymoma.