Abstract:The electromagnetic spectrum is the sixth dimensional battle space after land, sea, air, space and cyber, and runs through the other five dimensional battles. In order to effectively deal with the challenges and threats of the electromagnetic spectrum, the US Department of Defense puts forward the concept of electromagnetic spectrum operations, which has a profound impact on future combat patterns and even war forms. From the perspective of electromagnetic spectrum application, the application status and representative work of the US Department of Defense on electromagnetic spectrum are systematically introduced. Firstly, the traditional military applications of the electromagnetic spectrum are systematically sorted out, such as communications, radar, signals intelligence, infrared sensors, electronic warfare, navigation warfare. Secondly, the emerging military applications of the electromagnetic spectrum are emphatically introduced, such as 5G communications, artificial intelligence applications, laser communications, directed-energy weapons, anti-UAV systems and emerging concepts. Finally, the strategies and policies of the electromagnetic spectrum made by the US Department of Defense are summarized, and some suggestions are put forward to strengthen the operational capability of electromagnetic spectrum.