The opening-up of an opencast system is fundamental in the structure of the mining and technical system (MTS) and the efficiency of the functioning and development of the MTS as a whole depends on the quality of the assessment of its functioning. The decision-making on the reconstruction of the mining and technical system and its subsystems in modern conditions cannot be based only on the basis of a comparison of the technical and economic indicators of the options. Decisions on the development of MTS should be made on the basis of measuring and evaluating the parameters and indicators of the elements of the opening-up of an opencast system and taking into account the requirements of the sustainable development concept, i.e. taking into account the technical, economic, environmental and social aspects of the consequences of decisions taken. However, most of the existing approaches do not allow a comprehensive assessment of all elements of the opening-up of an opencast system, which able to take into account the interrelation between the indicators of the MTS elements in terms of the sustainable development concept. In this paper, we analyzed the factors of the sustainable functioning and development of the MTS and the opening-up of an opencast system, the parameters and indicators for their assessment, as well as the decision-making methods used in the practice of operating the MTS subsystems. The system of parameters and indicators for evaluating the opening-up of an opencast system has been substantiated, taking into account five groups of factors for the functioning of MTS: technical, technological, economic, social and environmental. The use of the fuzzy AHP method for ranking the parameters and indicators of the opening-up of an opencast system is proposed. The methodology and calculation example of assessment of the sustainable development of the opening-up of an opencast system using the fuzzy AHP method are presented. The results of the ranking of the parameters and indicators of the openingup of an opencast system showed that the most significant parameters are economic efficiency, the productivity of the transport complex, social efficiency and environmental efficiency, and the indicators are total income, emissions of pollutants and working conditions of personnel. Using the approach proposed in the work to assess the opening-up of an opencast system will improve: the quality of the assessment of the elements of the opening-up of an opencast system for compliance with the requirements of the sustainable development concept; the effectiveness of decision-making on the design, operational and strategic planning of the MTS development, taking into account the coordination of economic goals with goals in the field of ecology and social development.