Background and objective DNA methyltransferase 1 (DNMT1) is one of the important molecules regulating DNA methylation. The abnormal expression of DNMT1 was associated with the methylation and inactivation of tumor suppressor gene and tumorigenesis. The aim of this study is to clarify the difference of DNMT1 expression between lung cancer tissues and corresponding normal lung tissues, to analyze the relationships between DNMT1 expression and clinicopathologic characteristics of lung squamous cell carcinoma and adenocarcinoma, and to investigate the correlation between the expressions of DNMT1 and β-catenin. Methods The expressions of DNMT1 and β-catenin were examined in 84 lung squamous cell carcinoma and adenocarcinoma tissues and corresponding normal lung tissues using tissue microarray and immunohistochemistry. Results The average positive rate of DNMT1 was significantly higher in 84 lung cancer tissues [(58.04±35.07)%] than that in corresponding normal lung tissues [(6.88±10.26)%](t=12.835, P < 0.001). The high expression of DNMT1 was positively correlated with adenocarcinoma histological type (r=0.365, P=0.001), poor differentiation (r=0.253, P=0.021) and lymph node metastasis (r=0.246, P=0.024) in lung cancer. The expression of DNMT1 was significantly correlated with the cytoplasmic expression of β-catenin (r=0.571, P < 0.001). Conclusion The high expression of DNMT1 was a common phenomenon in lung squamous cell carcinoma and adenocarcinoma. The high expression of DNMT1 was correlated with the malignant phynotype of lung cancer. DNMT1 may express coordinately with β-catenin in lung cancer.