Posttraumatic stress disorder (PTSD) is a kind of mental disorder that usually occurs in a delayed manner and lasts long after life-threatened traumas. Biological studies of PTSD showed that brain function, neurochemistry, genes are significant biological factors that may influence PTSD. Antidepressants is the first choice of drug therapy of PTSD while some other medicines are also efficacious, and some appropriate psychotherapy should also be contained in the treatment.