The issue of evaluating the effectiveness of the ecological system project using the "discounted payback period" criterion, which takes into account transformational changes in its life cycle model, is considered.The specific peculiarities of the life cycle of the ecological system project were studied, in which it is proposed to include, in addition to the generally accepted pre-investment, investment and operational phases, ecologically oriented phases. Regenerative and revitalization phases are conside red to be ecologically oriented, that is, during which actions aimed at reducing the eco-destructive impact of the ecological system on the environment are performed. In the regenerative phase, an ecological product is created, which includes a complex of logistics services for the promotion of reverse recycling-utilization and related flows. The revitalization phase should end with the revival of the ecosystem damaged as a result of the creation and functioning of the ecological system.The phases of the life cycle are divided into stages, between which serial and parallel connections are established. The life cycle of the project is divided into time intervals during which from one to three stages of different phases of the project can proceed in parallel. A model of the life cycle of the ecological system project was developed, which shows the relationships between time intervals and cash flows corresponding to the phases of the project life cycle. A mathematical formula for calculating the discounted life of the project is proposed, which takes into account the specific features of the formation of cash flows of individual phases of the life cycle of the ecological system project. The application of the formula is possible when the assumption of constancy of cash flows of the stages of operational and regenerative phases is fulfilled, which corresponds to the impossibility of their exact forecast at the beginning of the project.Functional dependencies between the discounted payback period and cash flows during the phases of the project's life cycle were studied. Depending on the phase of the life cycle, the dependence is expressed as a linear, polynomial or power function. The detection of functional dependencies allows to study the dynamics of changes in the discounted payback period in response to changes in the project's cash flows, which can be used to predict the effectiveness of the ecological system project.