Abstract: In recent years, the Public-Private-Partnership (PPP) has been highly valued by the state and has been vigorously promoted. While the scale of PPP projects has expanded rapidly, there have been disadvantages, such as the difficulty of measuring project risks and the unreasonable risk sharing mechanism. Combining the characteristics of PPP projects, this paper first analyzes the principal-agent relationship between the government and social capital, and clarifies the influencing factors of PPP project risk cost calculations. This paper further constructs the risk cost measurement model under the two situations of information symmetry and information asymmetry and solves and analyzes the model. Then this paper verifies the model through an actual case and finally puts forward measures such as introducing a reputation mechanism, establishing availability payment and operation and maintenance service fees fully linked to performance evaluation results to reduce project risk costs, and finally promote the standardized development of PPP projects.

Key words: public-private-partnership (PPP), principal-agent, risk cost, performance appraisal