Recent studies suggest that polypeptide signals, such as systemin, RALF, PSK, ENOD40, SCR, CLV3, regulate plant growth and development process as well as plant responses to the environment. Most of the receptors of the polypeptide signals in plants are identified and the procession, release and signal transduction of the polypeptides show high similarity to those in animals and yeast. The possible roles of polypeptide signals in plants and the future prospects in this area are discussed.