The study’s purpose is to investigate the adolescent’s PTSD after earthquake had rose 6 month, discuss the relationship among Social Support, Big five personality and PTSD, Depression, Anxiety, and explore the social support’s moderating effect. The study selects 933 Sichuan province’s middle school students as participants, using IES-R, SSRS, NEO-FFI and depression, anxiety subscale of SCL-90 to investigate the adolescent’s PTSD. The results show that:(1) After 5.12 earthquake had rose 6 month, about 67.6% adolescents suffer PTSD or partial PTSD, the number of boys are more than girls, the number of grade one are the biggest, PTSD and Non-PTSD have significant effects on the N,E,A,C and Social support’s using. (2) The ratings of Depression and Anxiety are about 11.4% and 9%, the rating of Depression, Anxiety and PTSD is 7.2%. (3)Boys and girls have significant difference in Depression, girl’s score is higher than boys. Intrusion, Avoidance, IES-R score have significant difference in grade, the score of Intrusion, Hyperarousal, IES-R in grade 3 are the highest, the score of Depression and Anxiety in grade 4 are the highest. (4)IES-R score, Intrusion, Avoidance, Hyperarousal, Depression and Anxiety can be explained by N. IES-R score, Intrusion, Hyperarousal, Anxiety can be explained by A. Depression can be explained by O. (5) Social Support have mediation effect in the relationship between Big five Personality and Avoidance, between Big five Personality and Hyperarousal, between Big five Personality and IES-R score, between Big five Personality and Depression.(6) Big five Personality have main effect on IES-R score, Intrusion, Hyperarousal, Depression and Anxiety. This finding provided the conclusion that the social support haves moderating effect between the adolescent’s Post-traumatic stress disorder and Big five personality.