Private participation is the key element in forming public private partnership (PPP). Numerous studies have identified the factors of private participation in infrastructure projects, but previous results rarely focused on the willingness to participate in infrastructure PPP projects from the private sector's perspective. This research examines the factors of the private participation in PPP when considering willingness to participate as a function of internal (i.e., a firm's nature) and external factors (i.e., institutions, government behavior, and project characteristics). Using the logistic regression model and the data from the questionnaire survey, this research finds that nine variables have a significant coefficient, i.e. profitability, political connection, government intervention, government support, project complexity, and project experience; especially for those companies with more project experiences, political connection and higher profitability are more likely to be willing to participate in PPP projects. In contrast to previous studies, the research finds no support for the effect of institutional environment and public support on firms' willingness to participate in PPP. These findings can serve as a valuable reference in shaping the private sector's motivation to participate in PPP. Factors of private participation in PPP projects are explained and discussed in the context of the Chinese PPP experience and practice.