Hydrogen sulfide (H2S), which is well known traditionally as a toxic gas, has been proven to be produced endogenously by 3 enzymes in mammalian tissues and plays important roles in physiological and pathophysiological conditions. In the central nervous system, H2S functions as not only a neuromodulator, but also a neuroprotectant against oxidative stress. In the cardiovascular system, H2S relaxes vascular smooth muscles by the activation of KATP channels and inhibits smooth muscle cell proliferation via the mitogen-activated protein kinase signaling pathway. These effects are important for maintaining blood pressure and preventing vessel structural remodeling, and identifies H2S as an important factor in the development of some vascular diseases, such as hypertension. H2S also shows cardioprotective effects in ischemic myocardium and septic and endotoxin shock. Recent studies have demonstrated a new mechanism to explain the motor effect of H2S on the rat detrusor muscle, which is through the activation of the capsaicin-sensitive primary neuron. This review focuses on the recent research achievements on H2S and discloses the great potential of H2S as the third gaseous transmitter in cardiac protection.