Abstract: Nowadays, PPP (public-private partnership) scheme has been widely applied in the worldwide. However, this scheme is much-maligned due to cost overruns and poor operational performance etc. Adverse selection of private investors is one of the important reasons for the poor performance. Usually, adverse selection of investors mainly occurs in the procurement stage of PPP projects. It refers that investors without enough strength obtain franchise, seriously constraining the sustainable development of PPP schemes. In order to curb such behavior, the screening mechanism during the procurement phase of PPP projects is essential. Considering the bounded rationality of the governments and investors, a signal game model is constructed, quotation contents covering the construction cost, operation cost and discount rate of by investors and the reasonable profit rate by the governments. The results show that the camouflage cost of investors is the determinant for the PPP market to achieve the separating equilibrium. To save the inspection cost of the governments and achieve the separating equilibrium easily, sampling inspection mechanism is proposed to check on investors with low bids, followed by the optimal sampling ratio, in which scenario adverse selection of investors can be eradicated. To enhance a better understanding, a numerical example is presented to demonstrate the application of the models presented earlier. The findings of numerical simulation suggest that the optimal sampling ratio improves with the increased reasonable profit rate for high-capability investors, while decreases with an increasing camouflage cost, the punishment by the governments and the discount rate quotation by investors with high ability. Compared with the revenues, investors are sensitive to losses, but the degree of sensitivity decreases with the increased revenues and losses, which conforms to the prospect theory. The psychological factors of decision makers in the game process is analyzed, indicating that the introduction of the prospect theory makes the results more reasonable and has a good engineering application value. Eventually, to reduce adverse selection of investors in PPP projects, some recommendations are proposed, providing a reference for the governments and investors and helping improve the governance system of schemes.

Key words: PPP projects, adverse selection of investors, signal game, prospect theory