The article deals with the problem of constructing a conceptual model of intersystem accidents in the life support systems. Accidents in such systems lead to large-scale and long-term negative social, material, financial and ecological consequences. Particularly severe consequences are associated with the intersystem accidents when the termination or limitation in functioning affects two or more life support systems. The performed analysis showed that up to now much attention was paid to the simulation of emergency processes in the separate (no more than two) interacting systems. Among the main problems that make it difficult to simulate the emergency interaction of two life support systems and more, are the need to consider different dynamics of the propagation of emergency disturbances in the systems, as well as the complexity of formalizing the function of transferring disturbances between the systems. In this regard, research was initiated aimed at developing a conceptual model of the interaction of life support systems, which is a preliminary stage in the creation of appropriate formalized models. The paper formulates the requirements for the composition of the initial data: a description of the urbanized territory, with respect to which the intersystem accidents are considered; a block diagram of the interacting systems; types of interconnections of life support systems; scenarios of intersystem accidents; accident statistics, etc. It is shown that the multidimensional matrix of interactions can be a formal representation of the relationships between the systems in the event of occurrence of the intersystem accidents. When modeling the interaction, it is required to consider the inertia of the systems, for example, by introducing the coefficient of inertia, which will determine the delay in the transmission of the disturbance. The article formulates the main provisions and the schematic diagram of the conceptual model of intersystem accidents, as well as defines the basic requirements for the formal model. © 2021, STC Industrial Safety CJSC. All rights reserved.