Objective     To explore the changes of brain’s default network in patients with post-traumatic stress disorders (PTSD).     Methods     Resting-state functional magnetic resonance imaging (fMRI) was performed in 9 patients with PTSD and 10 healthy volunteers. Independent component analysis (ICA) was applied to separate the brain’s default network of all the subjects. Two sample t-test was used to analyze the difference of the brain’s default network between the patients and the healthy controls.     Results     A decreased functional connectivity was detected in the left anteromedial frontal lobe and the cingulate gyrus of the patients with PTSD

while an increased functional connectivity was detected in the precuneus.     Conclusion     Functional connectivity changes of the brain’s default network in patients with PTSD  provide a sensitive biological signal for imaging diagnosis of PTSD.