Considering the importance of the Islamic lifestyle in all aspects of life from the point of view of the Islam, the purpose of this study was to explaining the mediating role of islamic life style in the relationship between of psychological capital and belief development in students. In this descriptive-correlational study, from among all students of various schools of Allameh Tabataba’i University in 2017-2018, 378 students (231 women and 147 men) were selected using multistage cluster sampling. The participants completed the scale of belief development (SBD), psychological capital questionnaire, and islamic life style test. Pearson correlation coefficient and path analysis method were used for data analysis. The results of Pearson correlation coefficient showed that there was a significant positive correlation between the self-efficacy, hope, resiliency, optimism and Islamic life style with Belief Development (P>0/01). Path analysis also showed that the basic research model was suitable for GFI، AGFI، CFI، NFI، PNFI، TLI indices, and Islamic Lifestyle had a mediatorial role in the relationship between Psychological Capital and Belief Development.  Regarding the results of this study, it can be concluded that the importance of Psychological Capital and Islamic Life style in increasing the Belief Development, therefore, should be improved the Psychological Capital and Islamic Life style with appropriate training in students.