The paper conceives a conceptual model for public project management, based on the analysis of the relationship between public projects and market, and of the multilevel principal-agent chains of public projects.As public projects' multi-tiered principal-agent chain has its particularities,authors hold that the management structure of a public project shall reflect stakeholders' joint management efforts. The conceptual model, as an integrated system, takes into account varieties of elements, including internal inspection, external market inspection and government supervision.