Abstract: Toxin-antitoxin (TA) systems widely exist in the genomes and plasmids of prokaryotes． They are composed of two basic elements: stable toxins, whose role is to inhibit key progresses related to bacterial growth such as DNA replication, mRNA stability, protein translation and metabolic regulation, and unstable antitoxin antagonizing toxins． Under certain conditions, antitoxin is degraded or loses antagonistic function against cognate toxin, so that the toxin could inhibit cell growth． Eight types of TA systems have been discovered thus far, each with different mechanisms of action, and participating in the regulation of various biological activities． TA systems play important roles in bacterial stress response, resistance to bacteriophages, bacterial persistence, formation of drug resistance in pathogenic bacteria． TA systems have been used as tools to develop novel biotechniques both in scientific research and disease prevention and treatment．