Abstract: When analyzing the reliability of a large-scale and complicated structural system, the principal task of reliability analysis on the structural system is identifying the failure modes of the structural system. Aiming at the difficulties of identifying the failure modes of a large-scale and complicated structural system, one program for the failure mode identification of a transmission tower system is presented, based on the stage critical strength branch-and-bound principle. This program takes the advantage of the efficient visual modeling and finite analysis function of ANSYS and combines with the characteristics of MATLAB including powerful scientific computing and being easy to form a programming interface. Finally, this program is successfully used in the analysis of a practical engineering case, the results prove that this program is effective and feasible for identifying complicated structural failure modes and provide a basis for the reliability analysis of a transmission tower system.