Objective   It is difficult to localize multi-DOF systems directly using theoretical analysis. Therefore, this paper will use the equivalent method of single pass band approximation to localize the multi-DOF system.

  Method  The beam model is taken as the research object to conduct localized research. The localization factors of beams with unequal spacing arrangement are predicted using the equivalent method of single pass band approximation. A comparison between the localized factor prediction results of the equivalent method and the results of the statistical perturbation method verifies the correctness of the equivalent method. The validity of the equivalent method is verified by the FEM example of a beam with unequal spacing arrangement.

  Results   The results show that it is feasible to localize the multi-DOF system with the equivalent method of single pass band approximation.

  Conclusion  This method effectively avoids the difficulty of complex analysis of multi-DOF system, and realizes the engineering application of localized quantitative analysis of multi-DOF system.