The purpose of the article is to characterize public participation as the basis of democracy and sovereignty of state. The work uses sociological, formal legal, systemic methods, methods of analysis and synthesis, interpretation of legal norms. The article reveals democracy as a condition for the existence of the state, the legal nature of public participation and provides a terminological analysis of the concept of public participation. The institution of citizens' participation in ensuring the sovereignty of the state is a general legal element necessary for any state. The participation of citizens in ensuring the sovereignty of the state is a form of democracy, expressed in the state-significant activities of citizens aimed at ensuring the protection of the state. The grounds for participation are, firstly, patriotism, the spiritual and moral component of the constitutional duty, and secondly, the intention to protect against massive violations of rights and freedoms, aggression, and ensure their legitimate interests.