As a cross-domain operational domain spanning both traditional and non-traditional security fields, electromagnetic space has become a strategic commanding height in the competition for national security. The capability of electromagnetic space security system is regarded as a core variable reshaping the pattern of warfare and determining the right to victory. The evolution of the concept of electromagnetic space security is systematically reviewed, and the ‘three-dimensional’ leap characteristics displayed in its development process was summarized. A system architecture of electromagnetic space security and its essential connotations were proposed based on multiple perspectives. The current development status and technical challenges of electromagnetic space security were expounded. Some countermeasures and suggestions with multi-level and highly targeted were proposed for promoting the construction of the electromagnetic space security technology system. It provides the theoretical and practical references for safeguarding national electromagnetic space sovereignty and electromagnetic space security.