Abstract: Objective To investigate the expression of Bcell translocation gene 1（BTG1） in nonsmall cell lung cancer（NSCLC） and its biological effect in NSCLC cell line by BTG1 overexpression. Methods Immunohistochemistry and Western blotting were used to detect BTG1 protein expression in 82 cases of NSCLC and 38 cases of adjacent normal lung tissues， and the relationship between BTG1 expression and clinicopathological characteristics was analyzed. BTG1 lentiviral vector and empty vector were respectively transfected into NSCLC H1299 cell line. Quantitative realtime RTPCR（qRT-PCR） and Western blotting were used to detect the mRNA and protein level of BTG1. MTT assay， flow cytometry and Transwell assay were also used to detect the effects of the upregulated expression of BTG1 on H1299 cell proliferation, apoptosis and invasion. Results The positive expression rate of BTG1 protein was 37.8%（31/82） in NSCLC tissues, significantly lower than 84.2%（32/38） in adjacent normal lung tissues（P＜0.05）. The relative amount of BTG1 protein in NSCLC tissues was 0.331±0.035, significantly lower than 0.673±0.072 in adjacent normal lung tissues（P＜0.05）. The level of BTG1 protein expression was correlated with lymph node metastasis， clinical stage and histological grade（P＜0.05）. The result of biological function had shown that H1299 cell transfected BTG1 had a lower survival fraction， higher cell apoptosis， and significant decrease in migration and invasion， and lower Bcl-2， MMP-9 protein expression compared with H1299 cell untransfected BTG1（P＜0.05）. Conclusion BTG1 expression is decreased in NSCLC tissues， suggesting that BTG1 may play an important role as a negative regulator to NSCLC H1299 cell by promoting degradation of Bcl-2 and MMP-9 protein.