Objective:　To　investigate　the　protective　role　of　microRNA-27b　(miR-27b)　in　septic　cardiomyopathy　(SCM)　and　its　regulatory　mechanism　on　the　mitochondrial　fission　factor　(Mff)/mitochondrial　antiviral　signaling　protein　(MAVS)　axis.　Methods:　Transcriptome　data　from　septic　patients＇　cardiac　tissues　(GSE79962)　were　analyzed.　Serum　miR-27b　expression　was　measured　in　SCM　patients　(n=11),　sepsis-only　patients　(n=22),　and　healthy　controls　(n=30).　Mouse　SCM　model　and　HL-1　cardiomyocyte　model　were　established　by　lipopolysaccharide　(LPS)　induction.　The　molecular　mechanism　was　investigated　using　miR-27b　agonist/antagonist　and　Mff　intervention,　combined　with　RT-qPCR,　Western　blot,　immunofluorescence,　and　transmission　electron　microscopy.　Results:　Bioinformatics　analysis　revealed　significant　downregulation　of　miR-27b　in　SCM　cardiac　tissues　(log2FC=-3.9,　P＜0.001).　Clinical　validation　showed　lower　miR-27b　expression　in　SCM　patients＇　serum　compared　to　sepsis-only　patients　and　healthy　controls　(P＜0.05).　LPS-induced　SCM　model　exhibited　cardiac　dysfunction,　myocardial　injury,　mitochondrial　abnormalities,　decreased　miR-27b　expression,　and　increased　Mff　and　MAVS　levels.　miR-27b　targeted　Mff　to　maintain　mitochondrial　homeostasis,　thus　attenuating　LPS-induced　cardiomyocyte　inflammation　and　apoptosis,　while　Mff　overexpression　reversed　this　protective　effect.　Conclusion:　miR-27b　alleviates　myocardial　injury　and　inflammation　in　SCM　by　targeting　the　Mff/MAVS　axis　to　maintain　mitochondrial　homeostasis,　representing　a　potential　novel　therapeutic　target　for　SCM.