Abstract: Objective:To explore the effects of aerobic exercise training on the cardiac structure and miRNAs, and analyze their role in cardiac adaption induced by aerobic exercise training.Methods:Male KM mice (n=10/group) were randomized into two groups:8 weeks aerobic exercise training group and sedentary control group.Mice in training group undertook a swimming protocol for 8weeks, 5days/wk, from the 1st to 5th week, mice were trained one time a day in the morning, from the 6th to 8th week, mice were trained twice a day with a 12hinterval.In the 1st week, the training time was 30 min, and the time was increased 10 min per week until to 90 min.After the aerobic exercise training, all mice were measured by echocardiography.MiRNAs analysis was performed by miRNA microarray and confirmed by real-time PCR.The level of connective tissue growth factor (CTGF) gene expression was determined by real-time PCR, CTGF protein concentration was assessed by ELISA.Results:Aerobic exercise training improved aerobic capacity, left ventricular and induced cardiac hypertrophy.MiRNAs1and 133awere siginificant downregulated in training group (P<0.05) , however, miRNAs29cand 30cexpression increased in training group (P<0.05) , correlated with a decrease in CTGF gene expression in training group (P<0.05) .Furthermore, miRNA-30cwas inversely correlated to CTGF protein contration in training group (r=-0.818, P<0.05) .Conclusion: Aerobic exercise training could increase miRNA-30cexpression and decrease CTGF gene expression and concentration in the heart, which is relevant to the improved left ventricular compliance and beneficial cardiac effects.