To guarantee the supply of water conservancy PPP projects, the incentive mechanism of water conservancy PPP projects is established based on the principal-agent model under asymmetrical facilities by analyzing the gaming between the governmental departments and the private sectors. Then the optimal supply and the maximum utilities of the government and the private sectors are derived. Finally, three suggestions, including raising the efforts, reducing costs and risks of the private sectors, are put forward so as to provide theoretical foundation for supply of water conservancy PPP projects.