The emitter and threat level evaluation can provide a basis for configuring jamming resources and mission of assignment, and is a vital research subject of the airborne active self-defense electronic countermeasure. Aimed at the problems that the assessment indexes are few and incomprehensive, this paper establishes an emitter-threat assessment system to the needs of effect on the distance estimation index, resolution estimation index, probability estimation index and platform index. The paper calculates each index through parameter set. Then, the paper uses the grey correlation based on the entropy weight to figure out the optimal correlation degree. Finally, the paper judges the threat level by comprehensive relative closeness coefficient. The simulation example shows that though analyzing the result and comparing the method among other three methods, the merits prove the effectiveness and the feasibility of the method.