The factors affecting the threat level of the target are analyzed in amphibious assault ship (AAS) to air self-defense.And the attribute values of each factor are quantified.The weights of each factor are determined by combination weighting method based on entropy eveluation method and analytic hierarchy process (AHP).According to the weapon performances of AAS and the situation at that time,the incoming air targets are further divided into four categories.On this basis,the threat assessment model of AAS to air self-defense is established.Finally,two typical situations are designed for simulation calculation and the results show the model is economic.