Abstract: Objective 　To investigate the effects of exogenous MT1H gene stably transfection on growth of lung adenocarcinoma cell A549 in vitro. Methods 　A recombinant eukaryotic expression plasmid pcDNA3. 1 (-)-MT1 H was const ructed and transfected into A549 cells by lipofectamine 2000. Positive monoclone was screened by G418. RT-PCR and Western blot assays were used to identify the expression of MT1H mRNA and protein respectively. The cell proliferation was determined by MTT assay. The alterations of cell cycle were determined by flow cytomet ry ( FCM) . Then the expression of cyclinD1 mRNA was determined by RT-PCR. Results 　MT1H mRNA and protein were expressed in A549 cells. Cells tranfected pcDNA3. 1 (-)-MT1 H compared with the cont rol groups, proliferation rate significantly enhanced, cells number of G₀ / G_l phase obviously decreased while cells number of Sphase increased, cyclin D1 mRNA levels elevated. Conclusion 　MT1H could promote proliferation of lung adenocarcinoma cell A549 by up-regulating expression of cyclin D1 to facilitate cells into Sphase.