## 1 Introduction  
Studies on electromagnetic environmental effects (E3) can be traced back to the 1930s in the United States. Moreover, a milestone definition of electromagnetic environmental effects was given in the MIL-STD-464 [1] in March 1997. During and after this period, the concept evolved continuously until a nearly consistent definition was given in the JP1-02 [2] in 2008. In China, the concept of electromagnetic environmental effects has been defined in the GJB72A-2002 [3] and GJB1389A-2005 [4] as follows: the influence of the electromagnetic environment on the operation ability of electrical and electronic systems, equipment, and devices. Other countries largely follow the definition of the MIL-STD-464. From that definition, we can see that the study of electromagnetic environmental effects mainly focuses on various objects, which play a crucial role in certain fields [5].  
Generally, electromagnetic interference comes from two aspects. On the one hand, static electricity, lightning, and electromagnetic pulse in natural environments [6] will produce electromagnetic radiation. On the other hand, high-power frequency equipment will also generate harmonic interference signals during operation, making the surrounding electromagnetic environment extremely complex [7]. The equipment operating in the electromagnetic environment may have a blocking effect [8], a strong field effect [9], and other complex electromagnetic environmental effects that contribute to the interference. Eventually, this will lead to a loss of work efficiency. In agriculture, the growth of crops in an electromagnetic environment can be hindered [10; 11; 12]. The human body, when exposed to the electromagnetic environment, will also suffer from radiation [13; 14]. Therefore, more and more attention has been paid to the study of electromagnetic environmental effects. This study area has experienced a transition from effect modeling [15; 16] to effect evaluation [17] and prediction [18] and from qualitative to quantitative [19; 20] study. We believe that the study of the evaluation/prediction of electromagnetic environmental effects should not be limited to effects on a certain object. Even if the object does not exist, the electromagnetic environment may still exist. Hence, we can assess (or evaluate) the electromagnetic environment's complexity to predict its potential threat to equipment.  
For the evaluation, it is crucial to construct a reliable evaluation model to unify the objective and subjective effects and improve the adaptability and accuracy of the evaluation model in various complex electromagnetic environments. This review aims to mainly investigate the evaluation of the effects of electromagnetic environments from two perspectives: the electromagnetic environment and its interference effects on equipment. The modeling methods, input and output evaluation indexes, model performance, applicable conditions, and others related to the evaluation models are comprehensively reviewed. Additionally, future studies are also discovered according to current issues in electromagnetic environmental effects evaluation.  
In Section 2, there is an overview of the electromagnetic environmental effects assessment with an illustrated research architecture. In Section 3, we investigate the effects evaluation methods and models of the objective electromagnetic environment to understand the complexity of this environment and the relationship between the electromagnetic environment and the equipment in it. In Section 4, we survey research on the subjective electromagnetic environment. We show the evaluation methods and various evaluation models. In Section 5, we review the development of the effects evaluation systems. In Section 6, we discuss current research issues and future challenges to offer further research references to researchers. In the last section, we conclude this review.