Aiming at improving the knowledge management in PPP projects, the development of an ontology-based knowledge base for Residual Value Risk (RVR) in PPPs was conducted. Through literature review and typical case study of knowledge management in PPP projects, the RVR in PPP projects was analyzed from the perspective of risk structure, risk process and vulnerability, based on which the formation mechanism of RVR was explored. The RVR was deconstructed into five risk consequences. Furthermore, an improved RVR framework was established as a platform for organizing all kinds of knowledge for RVR in PPPs. Meanwhile, in order to express knowledge more effectively and promote their sharedness and transferability, the knowledge base was built by means of Ontology. Finally, the ontology editing software Protégé was used to build ontology-based RVR knowledge base, to achieve a more in-depth data processing function. The study can be used to analyze risk probability and vulnerability for both of public and private sectors in PPPs.