This paper was to explore the impact of positive leadership, trust on organizational citizenship behavior. The study method used in this study is a survey. The participants included 285 student affairs clerks from the southern university in Taiwan. The empirical results using structural equation modeling(SEM) indicate (a) the perceptions of positive leadership for student affairs staff have not significant impact on organizational citizenship behavior; (b) the perceptions of positive leadership for student affairs staff have a positively significant impact on trust; (c) the perceptions of trust for student affairs staff have a positively significant impact on organizational citizenship behavior. (d) the trust between positive leadership and organizational citizenship behavior has a positively significant mediating effects. Finally, based on these research findings, some discussions and recommendations for theory and practice on student affairs and future relational study would be given.