The current threat evaluation methods need to determine the weights of all evaluating indexes, which depends greatly on experts experience. To solve the problems, a catastrophe decision-making method is proposed for target threat evaluation. The method explores the influence factors of the threat degree, and a multi-layer evaluation index system is built up based on the primary and secondary relations of all factors. Then, primary catastrophe patterns of all sub-layer indexes and its upper layer indexes are established based on catastrophe theory, and catastrophe membership function value of sub-layer indexes are calculated using the normalization formulae, to describe the influence degree of sub-layer index to upper layer index. Then, catastrophe membership function value of upper layer indexes are calculated based on catastrophe decision-making principles. Finally, the total catastrophe membership function value of top index is calculated out, and the result is used for threat degree sequencing and decision-making. The method has rigorous theoretical foundation, concise and efficient calculating progress, and it is unnecessary to compute the weights of all indexes. The feasibility and effectiveness of the method is verified by the result of an actual calculating example.