Purpose Lung cancer is a relatively common type of cancer, and the incidence rate has been on the rise in recent years. MicroRNAs are a class of endogenous small RNA molecules, which are essential for the posttranscriptional regulation of genes. miR-29b is closely related to the occurrence and development of tumors, including prostate cancer, colon cancer, and breast cancer. However, few studies have been performed to explore the expression and pathway of miR-29b in non-small-cell lung cancer (NSCLC). Methods Using bioinformatics analysis, we found that patients with low relative expression of the miR-29b gene have a low long-term survival rate. The results of in vitro research showed that when miR-29b expression was upregulated, the invasion, migration, and proliferation of A549 and NCI-H-1792 cells was inhibited, and the apoptosis was accelerated. Results The results showed that FEM1B is a miR-29b target gene, and the expressions of FEM1B and miR-29b were negatively correlated. Like the upregulation of miR-29b expression, silencing the FEM1B expression could also impair the invasion, migration, and proliferation abilities of A549 and NCI-H-1792 cells. When FEM1B expression was restored, the inhibitory effect of miR-29b could be reversed. Reverse transcription-polymerase chain reaction (RT-PCR) and western blot (WB) analysis showed that overexpression of miR-29b could inhibit the expression of FEM1B, AKT, vascular endothelial growth factor (VEGF), and Sirt3 in A549 and NCI-H-1792 cells and upregulate the expression of FOXO1 protein. Conclusion The results of this study indicate that miR-29b inhibits the proliferation and deterioration of NSCLC cells by targeting FEM1B and inhibiting the activation of the FOXO1/AKT pathway. miR-29b may become a new target for the clinical diagnosis and treatment of lung cancer, and it is expected to become a new inhibitor of NSCLC.