The purpose of this study was to examine the relationship among social capital in festival organizations and volunteers` organizational commitment and organizational citizenship behavior(OCB). The four hypotheses were tested on data collected from 407 volunteers and analyzed using SPSS 20 and AMOS 20 in the manner of EFA, multiple regression analysis and SEM. As a result of the EFA, the construct validity of each variable of social capital was ensured. However, the validity of continuance commitment among the three sub-dimensions of organizational commitment was ensured by removing three metrics. OCB initially consisted of five sub-dimensions, but was collapsed as four dimensions. The results of the hypothesis is as follows: (1) the social capital affect OCB positively, especially networks positively affected all of sub-dimensions of OCB, (2) the social capital affected affective commitment and normative commitment positively, but continuance commitment negatively, (3) except continuance commitment, affective commitment and normative commitment were verified to play a mediating role between social capital and OCB. The result of this study could provide festival organizers insights of managing volunteers, they have to focus on strengthening networks in organizations and work on increasing volunteers` affective commitment and normative commitment for the success of their festivals.