The global prevalence of heart failure is still growing, which imposes a heavy economic burden. The role of microRNA-146b (miR-146b) in HF remains largely unknown. This study aims to explore the role and mechanism of miR-146b in HF. Method: We applied reverse transcription-polymerase chain reaction to search for differential microRNAs between myocardial tissues of heart failure patients and controls. We also used reverse transcription-polymerase chain reaction to detect the miR-146b expression in primary neonatal mouse cardiomyocytes and mice models of doxorubicin-induced HF. In vivo experiments, echocardiography was performed at baseline and weeks 6. After that we harvested mice's heart and evaluated the cardiomyocyte with hematoxylin and eosin (HE), Masson trichrome staining, and TUNEL staining. Through bioinformatics analysis, we found HIF-1α might be the target gene of miR-146b, which validated by luciferase reporter gene assay. Subsequently, mRNA and protein expression levels of HIF-1α were detected by overexpression or inhibition of miR-146b in primary neonatal mouse cardiomyocytes. Results: We found that miR-146b expression was decreased in myocardial tissues of HF patients compared with controls ( P < 0.01). MiR-146b levels were notably downregulated in HF models. MiR-146b knockout mice showed a more pronounced decrease in cardiac function and more severe myocardial fibrosis and apoptosis than wild type. Meanwhile, over expression or repression of miR-146b in primary neonatal mouse cardiomyocytes could inhibit or upregulate HIF-1α mRNA and protein expression. Conclusion : Our study shows that miR-146b may be a protective factor for cardiomyocytes by modulating HIF-1α.