Objective:To investigate expression of miR-638 and effects of miR-638 on apoptosis of lung adenocarcinoma cell line(SPC-A1). Methods:The expression of miR-638 in lung adenocarcinoma cell line was detected by real-time RT-PCR. Mimics of mir-638 were transiently transfected into SPC-A1 by using lipofectamine method. SPC-A1 cells were transfected with miR-638 mimics or non-special oligonucleotides(as negative control)or nothing(as blank control). After transfection,transfection efficiency was observed by fluorescence microscope. MiR-638 levels were detected by real-time quantitative RT-PCR. Cell apoptosis was detected by flow cytometry. Results:We observed that miR-638 was significantly inhibited in lung adenocarcinoma cells compared with that in normal cells. Cell apoptosis rate was increased significantly in cells transfected with miR-638(P <0.05)compared with negative and blank control cells. Conclusion:MiR-638 was poorly expressed in lung adenocarcinoma cells,and it could dramatically promote apoptosis of lung adenocarcinoma cells,thus provides a new target for the use of miR-638 in lung cancer biotherapy.