Objective To explore whether microRNA-203 (miR-203) targets and regulates the Toll-like receptor 4 (TLR4)/nuclear transcription factor kappa B (NF-κB)/nucleotide-binding oligomerization domain-like receptor protein 3 (NLRP3) to protect alveolar epithelial cells from lipopolysaccharide (LPS)-induced apoptosis and inflammation injury. Methods The alveolar epithelial A549 cells were used as the research objects and divided into: Control group (normal culture), LPS group (LPS treatment), LPS+miR-NC mimics group (LPS treatment after transfection of miR-NC mimics), LPS+ miR-203 mimics group (LPS treatment after transfection of miR-203 mimics), LPS+miR-203 mimics+pcDNA group (LPS treatment after transfection of miR-203 mimics and pcDNA), LPS+miR-203 mimics+pcDNA-TLR4 group (LPS treatment after transfection of miR-203 mimics and pcDNA-TLR4). Dual luciferase reporter gene was used to detect the targeting relationship between miR-203 and TLR4; Real-time quantitative reverse transcription-polymerase chain reaction was used to detect the relative expression levels of miR-203 and TLR4 mRNA; enzyme-linked immunosorbent assay was used to measure the levels of tumor necrosis factor-α (TNF-α), interleukin (IL)-1β and IL-6; flow cytometry was used to detect the apoptosis rate of A549 cells; Western blot was used to detect the expression of B-cell lymphoma/leukemia-2 gene (Bcl-2) and Bcl-2 associated X protein (Bax), TLR4, NF-κB and NLRP3 proteins in A549 cells. Results There was a targeted regulation relationship between miR-203 and TLR4. Compared with the Control group, the expression of miR-203, TLR4 mRNA and protein, Bax, NF-κB, and NLRP3 proteins in A549 cells in the LPS group increased, the levels of TNF-α, IL-1β and IL-6 in the cell supernatant increased, the apoptosis rate increased, the level of Bcl-2 protein in cells decreased (P<0.05). Compared with the LPS+miR-NC mimics group, the expression of TLR4 mRNA and protein, Bax, NF-κB, and NLRP3 proteins in A549 cells in the LPS+miR-203 mimics group decreased, the levels of TNF-α, IL-1β and IL-6 in the cell supernatant decreased, the apoptosis rate decreased, the expression level of miR-203 and the level of Bcl-2 protein in cells increased (P<0.05). Compared with the LPS+miR-203 mimics+pcDNA group, the expression of miR-203, TLR4 mRNA and protein, Bax, NF-κB, and NLRP3 proteins in A549 cells in the LPS+miR-203 mimics+pcDNA-TLR4 group increased, the levels of TNF-α, IL-1β and IL-6 in the cell supernatant increased, the apoptosis rate increased, the expression level of miR-203 and the level of Bcl-2 protein in cells decreased (P<0.05). Conclusion MiR-203 can target TLR4/NF-κB/NLRP3 to protect alveolar epithelial cells from apoptosis and inflammation induced by LPS.