Abstract：In order to explore the impact of contractual flexibility on project value adding in PPP projects. Based on incomplete contract theory and social exchange theory, a conceptual model including contractual flexibility, justice perception of private sector and PPP project value adding was constructed. Through a questionnaire survey, 234 valid data were obtained, and structural equation and Bootstrap methods were used for empirical test. The results showed that both the flexibility of contract terms and contract execution had significant positive effects on the value adding of PPP projects, and the three dimensions of private sector’s justice perception had the same effects. Justice perception of private sector significantly mediated the relationship between contractual flexibility and PPP project value-added, and the mediating effects of interactive justice and distributive justice were larger, and the one of procedural justice was the smallest.
