In order to ensure sustainable socio-economic development of the republic, strengthen the economy, develop the social sphere and identify areas of priority development a Strategy for the Long-Term Socio-Economic Development of the Republic of Mari El until 2030 was developed. The main goal of the development of the Strategy is to identify ways and means to ensure sustainable improvement of the welfare of the residents of the Mari El Republic, the dynamic development of economy of the Republic in the long term. Being one of the fundamental documents of the strategic planning system of the Mari El Republic that defines long-term socio-economic policy, the Strategy is formed on the basis of a bunch of principles analyzed in this work.?This study examines the main principles of the Strategy for ?socio-economic development of the Republic of Mari El for the period until 2030, analyzes the priorities, targets, tasks and areas of? socio-economic development of the Republic of Mari El (RME). It considers a set of system decisions of the Government of the RME for the long term period ensuring that the Republic of Mari El ?will become one of the most dynamically developing regions of the Volga Federal District in 2020-2030.