By means of fault tree analysis method, this paper gives a systemic analysis of the relevant factors which cause the fault of bird strike aircraft，and its fault tree is also established. Through qualitative analysis, 2580 minimum cut sets can be obtained. Expert estimation method, combined with fuzzy sets theory, is adopted to assess the happening probability of the base events. The calculating of “waste landfill attracting bird”—one of the base events of bird-strike-aircraft, is given as an example of this method. Through quantitative analysis, the happening probability of the top event is 0.00241, and the importance degree of all base events can be analyzed.