Abstract: Objective: To investigate the effect of perceived organizational support and psychological capital on psychological distress among psychiatric nurses. Methods: Eight hundred and twelve psychiatric nurses were recruited from six psychiatric hospitals of Shandong province. They were investigated with the Kessler Psychological Distress Scale, Survey of perceived organizational support, Psychological Capital Questionnaire. Results: About 70.3% of psychiatric nurses had psychological distress. The mean scores of psychological distress, perceived organizational support and psychological capital were 21.29±8.11, 37.17±11.07 and 4.09±0.70 respectively. Psychological distress was negatively related to psychological capital and perceived organizational support (P<0.01). Psychological capital had positive correlation with perceived organizational support (P<0.01). Psychological capital was a mediator (mediating effect was -0.11) of perceived organizational support and psychological distress; and it explained 29.1% of the total effects. Conclusion: Managers of psychiatric department should provide supportive settings and investment in psychological capital to improve psychological distress among psychiatric nurses.