Abstract: To diagnose transformer winding deformation and reveal its influence on voltage amplitude-frequency characteristics, this paper proposed a diagnostic criterion based on a hybrid multiconductor transmission line model and amplitude-frequency characteristic analysis. First, a hybrid multiconductor transmission line model with discs as units was constructed under high-frequency transient travelling waves, voltage transfer functions were solved via frequency-domain equations, and distributed parameters of normal and deformed windings were extracted using the finite element method. Then, the effects of radial and axial deformations on winding capacitance, inductance and amplitude-frequency characteristics were simulated. Results indicate that radial deformation shifts the extreme point frequencies by altering disc inductance, whereas axial displacement shifts the entire curve vertically by affecting end-disc ground capacitance. Additionally, a composite criterion integrating the correlation coefficient and extreme point variation was proposed to reflect both overall similarity and local distortion of the curve. Combined with measured characteristics of physical windings, thresholds for normal, slight, obvious and severe deformation states were established, offering a reliable quantitative basis for offline winding condition assessment.