〔Abstract〕 Objective To study the effect of miR-28-5p on cisplatin(DDP)-resistant A549 lung adenocarcinoma cell line(A549/DDP), and to explore whether its mechanism is related to ferroptosis suppressor protein 1(FSP1)-mediated ferroptosis. Methods The A549 lung adenocarcinoma cell line and A549/DDP cells were selected as the research objects. RT-qPCR method was used to detect the expression level of miR-28-5p in the cells. Cell proliferation was measured by CCK-8 method and colony formation assay. The target gene of miR-28-5p was identified and verified by luciferase reporter gene and Western blot analysis. A549/DDP was transfected with miR-28-5p simulant or FSP1 overexpression plasmid to evaluate cell proliferation, mitochondrial morphology was evaluated by transmission electron microscope, and the levels of reactive oxygen species(ROS), glutathione(GSH) and malondialdehyde(MDA) were measured by kit. A cell line-based xenograft model was established to evaluate the effect of miR-28-5p on tumor growthin vivo. Results Compared with A549 cells, the expression level of miR-28-5p in A549/DDP cells was significantly reduced(P<0.001). Compared with A549 cells, the cell viability(F=49.542,P<0.001) and colony forming ability(t=4.412,P<0.01) of A549/DDP cells increased significantly. Compared with miR-NC group, the cell viability(t=4.612,P<0.01) and colony number(t=4.503,P<0.01) of A549/DDP cells in miR-28-5p group significantly decreased. The luciferase activity decreased in the cells transfected with the miR-28-5p mimic, being significantly more so in the presence of the pGL3-FSP1 3′UTR-WT vector. In addition, the expression of FSP1 in cells overexpressing miR-28-5p was significantly suppressed. Compared with the Vector+miR-28-5p group, the FSP1+miR-28-5p group significantly increased cell viability and colony formation, cell mitochondrial length and GSH(P<0.01), and significantly increased cell apoptosis, ROS production and MDA formation decrease(P<0.05).In vivoexperiments showed that compared with the miR-NC+DDP group, the size and weight of tumors formed in the miR-28-5p+DDP group were significantly reduced(P<0.05), and the expression of Ki-67 and FSP1 protein was significantly reduced(P<0.05). Conclusion The mechanism of miR-28-5p reversing cisplatin resistance in lung adenocarcinoma cells may be related to the inhibition of FSP1-mediated ferroptosis.