The aim of the work is to develop a conceptual approach to decision support in assessing the functional state of a complex system of biological type. The definition of the functional state and the basic principles of its evaluation for complex systems of biological type on the basis of system representations are formulated. A situational model of the problem environment as a set-theoretic composition of the main components and evaluation functions was developed, which allowed to formulate the definition of the problem situation. The structure of the application of data mining to assess the functional state of a complex system using as feedback models of three levels-strategic, tactical and operational. A system of coordinated models for decisionmaking in assessing the functional state of a complex system based on causal representations in the form of Markov chains and Petri nets is proposed.