Abstract: Heart failure is a complex clinical syndrome and vascular dysfunction is one of the leading causes of heart failure. Relaxin is a human relaxin (serelaxin, relaxin-2) recombinant vasoactive peptide for systemic and renal vasodilation, and is one of the pharmacological treatments of acute heart failure. The clinical benefits of relaxin in the treatment of congestive heart failure can be attributed to improvement in the circulatory system, the heart, renal hemodynamics, protection of cells and organs from damage, effects of anti-inflammation, anti-impact, anti-fibrotic remodeling and anti-myocardial ischemia, promotion of angiogenesis, reduction of heart and kidney ischemia and hypoxia, and decrease of heart failure mortality. In this review, we focus on the role of relaxin and its mechanism and review clinical trials of relaxin in treatment of heart failure.