A project portfolio risk warning mechanism which includes horizontal and vertical twoway risk warning model is established. Project portfolio is divided into five stages of decisionmaking, preparation, development, implementation and completion, and key risks and key factors are identified for dynamic warning based on lifecycle attribute in horizontal mode. Vertical mode is built by opposite process of risk measurement, and three retrospective portfolio risk warning system is established. The excessive portfolio risks can be specific to particular project, interactions between two projects or management complexity factor.