As the most challenging issue in the field of the electromagnetic pulse effects, no uniform method of the system vulnerability assessment against the high-altitude electromagnetic pulse (HEMP) has been established. The system design, use and test organizations stand on the different perspectives and the different criteria, which lead to the severe discrepancy in the assessment results. On the other hand, the basic data come from several sources, such as the experience, testing, computation or, subjective judgements, and there is great uncertainty in these data. So the creditability of the assessment conclusions is vital to be validated from the objective and subjective information. However, the high cost and long duration will prohibit the conduct of the whole system test or computation, such as the communication and power infrastructures. Thus the assessment validation is a hard subject.

In this paper, vulnerability the of a computer control system to HEMP is taken as an illustration to validate the effectiveness of different assessment methods.

Here, three approaches relatively from the fields of the system use, design and test (i.e. risk analysis, electromagnetic compatibility (EMC) analysis and Bayesian networks (BN)) are adopted and independently evaluate the HEMP susceptibility of the item under test (IUT).

Three evaluation results indicate that the assessment methods are effective despite their different thoughts, emphasizes and knowledge fields.

The BN method can preferably respond to the inherent characteristic of HEMP effect assessments, such as the conductivity, uncertainty, synthesis and subjectiveness, so the BN method is potentially promising in the practices.