For the features in the evaluation indexes including quantificational and qualitative indicators, the paper uses priority degree evaluation method to evaluate threat of air attack targets. For many targets, via ascertaining evaluation index system, building dependent function of each evaluation indexes, accounting correlation degree and standardization correlation degree and accounting threat priority of each target, then sequencing each target. The example proves that the method is reliable and practical, supplying the quantificational basis for ascertaining the aerial defence missile-interception’s schemes.