Abstract: The research of opioid peptides already has a history of more than 30 years. Opioid peptides are a kind of neuroactive substances with hormone and neurotransmitter functions, which confers opioid peptides an important mediator to regulate the central nervous system and the peripheral organs. They can be divided into endogenous opioid peptides and exogenous opioid peptides. In 1970s, the opioid peptides with the morphine activity were found continuously both in vivo and in vitro, leading to an increased interest of scientists. Afterwards,scientists discovered that they played an important role in the nervous, immune and endocrine systems, for which they were called the neuroimmune peptides. A number of opioid peptides have already been discovered up to now. This article overviews the structure characteristics, the present advances and the physiologi-cal functions of opioid peptides and makes prospects of research in the future.

Key words: opioid peptide, structure, sequence, function, prospect