Pulmonary fibrosis (PF) may be reduced by inducing autophagy, and miR-128-3p could regulate cell autophagy through several methods, however, the mechanism is still unknown. In this experiment, whether miR-128-3p could regulate the bleomycin-induced autophagy of MRC-5 cells by regulating the PTEN/AKT/GSK3 beta/mTOR signaling pathway was explored. Bleomycin (10 mu g/mL) was used to induce MRC-5 cells in vitro and form a cell model of PF. The relative proliferation rate, activity, and autophagy rate of MRC-5 cells were detected using MTT, CCK-8, and GFP-LC3 fluorescence, respectively. The expression levels of LC3-II, Beclin-1, PTEN, p-Akt, p-GSK3 beta, and p-mTOR proteins in bleomycin-induced MRC-5 cells were determined via Western blotting. The expression levels of GSK3 beta mRNA and miR-128-3p were determined in bleomycin-induced MRC-5 cells through real-time polymerase chain reaction. The results showed that bleomycin decreased the autophagy of MRC-5 cells and increased the activity and proliferation rate of these cells. The miR-128-3p inhibitor inhibited the expression levels of p-Akt and p-mTOR, increased the expression levels of GSK3 beta, PTEN, LC3-II, and Beclin-1, and induced bleomycin-induced autophagy in MRC-5 cells. The results suggested that miR-128-3p overexpression could improve bleomycin-induced PF by increasing the bleomycin-induced autophagy of MRC-5 cells. The mechanism may be related to the decreased expression of GSK3 beta gene and protein by upregulating miR-128-3p expression.