Abstract: Aiming at the characteristic of electromagnetism environment （EME） that is complex, changeful, and difficult to describe in quantitatively and qualitatively, this paper analyses the meaning of the usual complexity and special complexity of electromagnetism environment （EME） in detail. This paper puts forward a novel method based D-S Evidence Theory to evaluate the special complexity of EME, according to the functional degrade of the electronic SYstem and performs an example validation. The method has a common guidance meaning to evaluate the usual complexity and special complexity of electromagnetism environment, which has satisfied the evaluation of above requirements in battlefield.