Based on characteristics of transportation infrastructure projects under a PPP model, an early warning risk index system for the private sector was put forward. The system is comprised of 15 indexes from five aspects, including risks associated with politics and law, economics, credit, construction and operation. An early warning risk model was constructed by applying fuzzy set theory and matterelement theory. The fuzzy set method helps calculate the weight and evaluation values for qualitative indexes, thereby avoiding the limitations of individual decisions. The matterelement method can evaluate comprehensive risks by using the comprehensive relations, is easy to use, and directly gives results. Further empirical research was conducted that verifies this method is scientific and applicable.