Topicality. The non-institutional methodology of environmental management based on the formation of the “institutional ecosystem” has been considered and scientifically substantiated. The scientific categories that provide its methodological integrity are substantiated: “institutional dominants”, “replicates”, “institutional players”, decomposition of these concepts within the framework of modern economic-ecological and neo-institutional theory, its connection in the context of the formation the national institutional model of eco-management. A number of institutional innovations (replicates) have also been proposed, in particular the requirements for updating Annex XXX to the EU - UA Association Agreement in the context of the development of the national eco-management system.Aim and tasks. The aim of the article is to discuss the challenge to institutional development for institutional ecosystem as a new paradigm of nature management development.Research results. Institutional ecosystem - a dynamic, balanced, sustainable, self-replicating, regulated system that is "comfortable" for the entities of institutional relationships that transact with each other, is also a source of institutional ecosystem formation (role of the entity), involved in its formation , development, regulation (through the formation of institutional discourse), consumption (through the use of part of the institutional environment under its influence) and acting on principles: Institutional prediction based on the transformation of institutional dominance; -Replication (timely exit from the "comfort zone" for institutional transformations and system fertility at different hierarchical levels; Incubation - ensuring the completeness of the institutional cycle. There is an institutional ecosystem equilibrium balance between institutional rules (dominant), conditions (subdominants). However, this situation is short-lived: In the current context, institutional dominance is changing rapidly. And the institutional ecosystem has to “adjust” internal institutional conditions (subdominants) in order to obtain a state of equilibrium (institutional homeostasis).Conclusion. 1. The ecosystem, as a scientific category used in economics, is primarily characterized by internal dynamics and development under the influence of internal and external factors. 2. The ecosystem is seen as a network consisting of elements, some of which are the largest and define ecosystem health; it is defined by the relevant dominant. 3. Cooperative and mutual aid processes play an important role in the functioning of ecosystems, regardless of the status and capabilities of their participants. This approach is completely in line with the basic tenet of the non-institutional economy on the support and role of "weak links".