Abstract: Focusing on the concepts of joint electromagnetic spectrum operations(JEMSO) proposed by U.S. DoD, this paper fully analyzes the related electromagnetic operational environment(EMOE) from the viewpoints of JEMSO, complex electromagnetic environment(EME) and electromagnetic orders of battle(EOB); then points out that the compositions of newly proposed EMOE are actually similar to that of the complex EME well known by us；finally, it shows with case studies the weird complexity of EMOE effects.