There could be multi-failure modes in the course of working of the structure system
including slender bar members. For example, strength failure, fatigue failure and buckling failure,
especially sudden buckling failure would bring large disaster to structure. In this paper, according to
Fatigue and Damage Mechanics theory, safe margin expression of the different failure mode of
structure (static strength, fatigue and buckling) is given firstly, then by analyzing different failure
mode of structural element under static and fatigue loads, and failure mode of the calculating
element is confirmed by comparing the failure probability value of different failure mode. In the
course of searching for significant failure paths, not only is failure mode that stiffness matrix of
structure is zero considered, but also buckling failure mode of compressed residual structure is
considered too, so that failure analysis is more reasonable. In the end, the reliability calculating
method of the structural system is given, and the validity of the method proposed in this paper is
explained combining an example.