OBJECTIVE To study the ameliorative effect and mechanism of Forsythia suspensa-Lonicera japonica herb pair on acute lung injury （ALI） based on serum exosomal microRNA （miRNA）. METHODS The rats were randomly divided into a blank group （normal saline）， model group （nomal saline）， and F. suspensa-L. japonica herb pair group （2.55 g/kg）， with 10 rats in each group. Except for the blank group， the other groups were used to establish an ALI model by intratracheal dripping of 5 mg/ mL lipopolysaccharides. After modeling， each group was given relevant medicine/normal saline intragastrically， once a day， for 3 consecutive days. After the last medication， the pathological status of lung tissue was observed； lung wet-to-dry weight ratio and leukocyte counts in bronchoalveolar lavage fluid （BALF） were determined. The levels of inflammatory factors [tumor necrosis factor-α（TNF-α）， interleukin-1β （IL-1β）， IL-10] in BALF were determined. Exosomes were isolated from rat serum， and high- throughput sequencing technology was employed to screen differentially expressed miRNA within the exosomes， followed by Kyoto Encyclopedia of Genes and Genomes （KEGG） enrichment analysis. Based on the screened differentially expressed miRNA and the enriched KEGG pathways， in vitro cellular experiments were conducted for validation. RESULTS The animal experimental results demonstrated that after intervention with the F. suspensa-L. japonica herb pair， the wet-to-dry weight ratio， the number of leukocytes in BALF， as well as the levels of TNF-α and IL-1β in BALF of ALI rats were all significantly reduced （P＜0.01）， while the level of IL-10 was significantly increased （P＜0.01）. The results of high-throughput sequencing experiments revealed that the F. suspensa-L. japonica herb pair could significantly up-regulate the expressions of miR-345-3p， miR-194-5p， miR-653-5p， and others in exosomes. Among them， the KEGG pathways involved in the target genes of differentially expressed miRNA included the hypoxia-inducible factor-1（HIF-1） signaling pathway， among others. The results of cellular E-mail：huang.haiying@126.com validation experiments showed that overexpressed miR-345-3p could significantly elevate the level of IL-10 in the cell supernatant （P＜0.01）， while significantly reducing the levels of TNF-α and IL-1β in the cell supernatant， as well as the mRNA and protein expression levels of protein kinase B1， phosphatidylinositol 3- kinase， and HIF-1α （P＜0.01）. CONCLUSIONS F. suspensa-L. japonica herb pair can alleviate inflammatory responses and thereby exert a therapeutic effect in improving ALI by up-regulating the expression of miR-345-3p in serum exosomes and inhibiting the activity of the HIF-1 signaling pathway.