<p>A novel segmented time-varying transformation stochastic resonance is proposed, and its use in extracting and enhancing weak misalignment fault features of the coupling under variable speed conditions is studied. At first, the theory of the segmented time-varying transformation stochastic resonance is described in detail. Numerical simulations are carried out to successfully extract the weak misalignment fault characteristic of a coupling. Then, based on the coupling misalignment fault test bench, the method is verified under different amounts of coupling misalignment and time-variable speed conditions. The results demonstrate that the method can effectively extract the fault feature under strong noise background and time-variable speed conditions. The proposed method has a certain engineering value in coupling misalignment fault diagnosis.</p>