The gene-encoded antimicrobial peptides (AMPs) are widely distributed in insects, plants, animals and the human bodies, and served as crucial components in the innate host defenses. In addition to their direct broad-spectrum antimicrobial activities against Gram-positive and Gram-negative bacteria, fungi, some enveloped viruses and parasites, AMPs also show multiple biological activities including antitumor activity, neutralizing endotoxin, anti-inflammatory activity, and chemoattracting memory T cells, monocytes and dendritic cells. AMPs play an important role in the integration of the innate and acquired immune responses, starting the acquired immune system, and enhancing the body against microbial infections. This article has reviewed the multiple biological activities, mechanisms of antimicrobial action and the application prospects of AMPs.［Chinese Journal of Animal Nutrition，2011，23（4）：546 -555］