<p>Identifying the weak stiffness positions of a machine tool is crucial for enhancing its overall structural rigidity. In 1high-value engineering structures such as machine tools or aviation fields, generating the data first by simulation is often necessary. Thus, the required model often corresponds to the actual working conditions. However, achieving an equal spacing sensor distribution during the actual measurement process in the actual damage identification project is often difficult because of the occlusion of the sensor position arranged by the measured structure. In damage identification, the identification indexes designed by equidistant sensor distribution often fail or have large errors. In this study, a damage identification index (<i>a</i><Stack> _<i>e</i> ^″ </Stack>) method independent of the distribution of equidistant sensors is proposed based on the flexibility curvature matrix. The element stiffness matrix and the element mass matrix for solving the flexibility curvature matrix are adjusted according to the actual sensor spacing, and the obtained flexibility matrix is calculated twice by difference to obtain a new damage identification index. A cantilever beam is employed as a reference to confirm the efficacy of the damage identification index via numerical simulation. Thus, the robustness of this damage identification index in identifying damage across various scenarios of damage and amidst noise interference is demonstrated. Further validation of the index utility is conducted on a gear grinding machine, thereby confirming its adaptability even with sensors spaced unevenly.</p>