Abstract: Maintaining electromagnetic space sovereignty and electromagnetic space security benefits the common interests of all countries in the world. This paper mainly raises and studies the significant theoretical issues of electromagnetic space sovereignty, elaborates on its existence as well as its concept and connotation from the perspectives of importance, objectivity and necessity, and analyzes the basis and content of the international law on electromagnetic space sovereignty. In addition, it discusses the relationship between electromagnetic space sovereignty and electromagnetic space security, and puts forward proposals on the measures to defend electromagnetic space sovereignty, so as to provide support for the formulation and improvement of national security strategies, regulations and policies in this field, and for the safeguarding of electromagnetic space sovereignty and security.