This study aimed to investigate the mechanism underlying the relationships among positive emotions, work well-being (job satisfaction and stress symptoms) and turnover intention based on the broaden-and-build theory (Fredrickson in Am Psychol 56:218–226, 2001) and conservation of resources theory (Hobfoll in Am Psychol 44:513–524, 1989; Rev Gen Psychol 6:307–324, 2002). A total of 311 Chinese police officers in Hong Kong were recruited in this study. Our results showed that, in line with previous studies, psychological capital (PsyCap) was composed of four dimensions, namely self-efficacy, hope, optimism and resiliency. Furthermore, we found that positive emotions were positively related to PsyCap; that work well-being (both job satisfaction and stress symptoms) fully mediated the association between PsyCap and turnover intention. In addition, positive emotions had a direct negative effect on stress symptoms. The theoretical and practical implications of the findings and issues for future research were discussed in the paper.