Heart is pumping throughout life of animals ever since embryogenesis. The mammalian heart consists of four chambers along with specialized myocardial system for electrical conduction and force production, which guarantees the heart to pump efficiently. miR-1, the cardiac specific mi RNA, is suggested to play essential roles in cardiogenesis and in regulating physiological function of heart. During early stage of cardio genesis, miR-1 promotes cardiac mesoderm induction. In the subsequent morphogenesis, miR-1 controls cell fate of various lineages and the balance between proliferation and differentiation so that cardiac chambers could develop normally. In postnatal life, miR-1 modulates atrioventricular and ventricular conduction at multiple levels and contributes to the formation of organized sarcomere. Advance in the role miR-1 plays in cardiac biological processes have put new perspectives on mechanisms of heart diseases.