Abstract: Objective The effects of miR-409-3p on the proliferation of non-small-cell lung cancer cell strain A549 were detected. Methods The control group was A549 cells of human non-small cell lung cancer cell line cultured under normal conditions. On the basis of the control group, the experimental group used chemical synthesis miR-409-3p mimetic and Liposome transfection to construct miR-409-3p high-expression lung cancer A549 cell strain; The expression of miR-409-3pmRNA, cell proliferation by MTT, apoptosis and cycle by flow cytometry after 48 H were observed. Results The expression of miR-409-3p mimic increased significantly in A549 cells after transfection, but decreased significantly in the control group. The percentage of total apoptosis was(22.66±4.61) %, which was significantly higher than that of the control group[ (7.78 ±1.95) %, P & lt; 0.05] :: The G0/G1 phase was(40.21±5.37) <UNK>, significantly lower than the control group cells[ (56.09± 5.22) %, P & lt; 0.05] The double fluorescence reporting system showed that the oncogene ELF2 was the target gene of miR-409-3p. After the expression of miR-409-3p mimic, the level of endogenous ELF2 protein expression decreased significantly. Conclusion MiR-409-3p may inhibit the proliferation and promote apoptosis of non-small cell lung cancer cells A549 by regulating the transcription level of ELF2.