G1000 integrated avionics system integrates many electronic components including navigation, communication, course, attitude and display etc, has been widely used in all kinds of civil aviation aircraft. In this paper, the fussy-sets theory is introduced briefly at first. Because the occurrence probability of fault event in G1000 system usually shows fuzzy and random feature, the fussy-sets theory is inducted into the fault tree analysis. Fuzzy information collected from faults occurring in various parts is processed. Fuzzy mathematics method is applied to calculate occurrence probability of the top event and the middle events. This method can solve the problems of fuzzy and uncertain fault events which traditional fault tree analysis can not deal with and provide reference for using, repairing and maintenance of G1000 system.