TA (Toxin-Antitoxin) systems are widely spread in chromosomes and plasmids of bacteria and archaea. These systems consist of two co-expression genes, encoding stable toxin and sensitive antitoxin, respectively. The toxicity of toxins usually inhibits bacterial growth and antitoxins can neutralize the toxins. Interaction between them would regulate the growth state of bacteria precisely. According to the composition of TA and nature of antitoxin, six types of TA have been found. The role of these TA systems in bacteria has been a hot research topic in recent years. Now, the research status on functions of bacterial TA is reviewed.