The aim of this study is to detect the expression profiles of SMAD1 protein in lung cancer tissues and normal tissues to investigate its effect on the incidence of lung cancer. The expression profiles of SMAD1 protein in 60 cases of lung cancer tissues (lung cancer group), 25 cases of normal alveolus tissues (alveolus control group) and 29 cases of normal bronchial tissues (bronchial control group) were detected by adopting immunohistochemical analyses, and their relationships with clinicopathologic data were analyzed. The expression of SMAD1 protein in the lung cancer group and the lung squamous cell carcinoma group was significantly lower than that in the alveolus control group and the bronchial control group (P < 0.01). The expression of SMAD1 protein in the lung adenocarcinoma group was significantly lower than that in the alveolus control group and the bronchial control group (P < 0.01); The expression SMAD1 protein showed a significant correlation with lung cancer differentiation and lymphatic metastasis (P < 0.05), but not with genders, ages, tumor sizes and histological types of lung cancer patients (P>0.05).