The aftermath of traumatic events differs from person to person. Although some people show negative results, many people report positive results such as Post-traumatic Growth(PTG). PTG refers to positive changes that result from individual struggle to deal with trauma and its psychological consequences. It contains three aspects such as perceived changes in self, changed sense of relationship with others, and changed philosophy of life. Recently, the overwhelming majority of research paid emphasis on the influencing factors of PTG, particularly the exploration of the development of PTG. But there are fewer researchers pay attention to the effect of emotion on PTG, and also fewer researchers explored the mechanism that’s development of PTG. According to the broaden-and-build theory of positive emotions, the gratitude can play an important role in the development of PTG. Based on the theory,many researchers carried out study in the relation of gratitude to PTG, and found that gratitude have predicted positively to PTG. Although theoretical and empirical studies researchers agreed that gratitude had effects on PTG, few studies have explored the role of others factors in the relationship between gratitude and PTG. According to relevant theories, the social support and deliberate rumination plays an important role in the process of gratitude affecting PTG. For this reason, the current study incorporate deliberate rumination and social support into the exploration of relationships between gratitude and PTG and the internal mechanism how gratitude affect PTG was also taking into much account . The current study used gratitude questionnaires, social support questionnaires, the event related rumination inventory and posttraumatic growth inventory to investigate 354 adolescents (165males, 189 females) of grade 8, 9 in junior schools and 11, 12 in senior high schools of Wenchuan county four and a half years after the Wenchuan earthquake. The main results were as following: (1) the level of gratitude, social support and PTG were medium, but the level of deliberate rumination was low. The most important was that all the variables have significantly positive relation. (2) Social support and deliberate rumination mediate partly the relationship between gratitude and PTG. On the one hand, gratitude can affect the PTG directly. On the other hand, gratitude can affect the PTG positively through social support and deliberate rumination, respectively. In addition, gratitude can affect the PTG positively via the indirect way which social support influences deliberate rumination. These results have some practical implications. That is, it necessary to improve adolescent gratitude level, and help them to gain more social support and promote them to more deliberate rumination to traumatic event, in turn guide adolescents to positive thought on self, other and world after trauma, ultimately promote the development of PTG.