Persistent separation from parents immediately after a natural disaster (such as earthquake or hurricane), along with the loss of the child’s home, pets, toys, and friends predicts post-traumatic stress disorder (PTSD) in children. Orphans reported significantly more PTSD symptoms than the disaster and non-trauma control groups. Research on orphans shows convincingly that psychological trauma has an enormously damaging effect on their development, their mental and physical health, as well as cognition and behavior. Intervention, in the form of administrative systems and psychological support, would be enormously valuable, both to the orphans and to society. However, the effectiveness and efficiency of intervention can be greatly improved with a better understanding of both PTSD's development, and its cognitive neural mechanisms. To this end, our project consists of 3 major goals: (1) use methods taken from epidemiology to characterize the trajectory of PTSD in post-disaster orphans; (2) investigate changes in cognitive development and immunological function in post disaster orphans in a cross sectional study, revealing the mental and behavior mechanism of PTSD; (3) examine the cognitive neural mechanism of the PTSD by using eye tracking and event-related potentials technologies. Using the results of this project, we can provide expert insight into psychological support for orphans, suggesting effective administrative systems and models of psychological support for orphans in emergency settings.