The electromagnetic spectrum has become an indispensable strategic resourc e for our country in this information era.Facing the major challenge brought by increasingly complex electromagnetic spectrum, the study of electromagnetic spec trum space has important significance for future spectrum sharing, radio order m a nagement and the war of electromagnetic spectrum. The paper focuses on theoreti cal model of spectrum situation, spectrum situation sensing in wide area, dynami c spectrum situation generating and efficient utilization of spectrum situation to study the basic theory and the key technology of electromagnetic spectrum spa ce cogniti on. Moreover, it is pointed out that the integration o f isolated, scattered and static spectrum data into a whole, dynamic, correlated and visible heterogeneous data set should be paid more attention to in the deve lopment of spectrum situation. It provides the theoretical and technical support for improving the dynamic spectrum efficiency, detection probability of maliciou s user, false alarm probability and the ratio of spectral efficiency.