In public-private partnership (PPP) projects, the private sector's performance is influenced by administrative efficiency, and the impact varies across different contractual dimensions. Existing research mainly focuses on the influence of project governance on project performance, with few scholars delving into the impact of administrative efficiency on the contractual dimensions of PPP projects. To address this gap, this study employs literature analysis to examine the contractual relationships among PPP project stakeholders, identifying four sub-dimensions: responsibility and authority allocation, profit allocation, risk allocation, and accountability. It then investigates the moderating role of administrative efficiency in the relationships between contractual dimensions and project performance, proposing hypotheses and constructing a research model. The findings reveal that all four sub-dimensions of contractual relationships exert significant positive effects on project performance. Specifically, administrative efficiency significantly enhances the positive relationship between responsibility/authority allocation and project performance, as well as between risk allocation and project performance. These results highlight the critical role of administrative efficiency in optimizing contractual mechanisms to improve PPP project outcomes, providing theoretical and practical insights for enhancing contractual governance in PPP projects.