Objective To explore the effect and the regulatory mechanism of miRNA-142-3p (miR-142-3p) in rat alveolar macrophage inflammatory response stimulated with lipopolysaccharide (LPS). Methods The rat alveolar macrophages NR8383 were stimulated with 100 ng/mL LPS, and the mRNA and protein expressions of miR-142-3p and high-mobility group box 1 (HMGB1) were determined by qPCR and Western blotting analysis after stimulating for 0, 6, 24 and 48 h. We then transfected the macrophage with miR-142-3p mimic in vitro and used qPCR to measure the mRNA expressions of miR-142-3p, tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), IL-1β and macrophage inflammatory protein 2β (MIP-2β). Western blotting analysis was used to measure the protein expression of HMGB1, and ELISA was used to observe the concentration of HMGB1 in cell culture fluid. Results The highest expression of miR-142-3p was found in NR8383 cells when stimulated with LPS for 48 h and the highest concentration of HMGB1 was noticed at 24 h stimulation, and they were significantly different from those at 0 h (P<0.05). After overexpression of miR-142-3p, the expression of miR-142-3p was significantly increased (P<0.05), and the expressions of HMGB1 protein and mRNA of HMGB1, TNF-α, IL-6, IL-1β and MIP-2β were significantly decreased (P<0.05). Conclusion miR-142-3p can mediate the NR8383 cell inflammatory response induced by LPS, which may be caused by negative regulation of HMGB1 expression.