With the development of the national economy, the scale of the power grid continues to expand. As an important part of power transmission, the short-circuit resistance of transformers determines whether the power grid can operate safely and stably. When the transformer winding is short-circuited, the instantaneous short-circuit current can reach several times the rated current. Although the winding can still operate under these conditions, it will inevitably deform slightly. After long-term operation, the slight deformation on the winding gradually accumulates into a deformation that cannot be ignored, which becomes a major hidden danger in the operation of the transformer. Therefore, studying the different compressive stress characteristics of transformer windings during a short circuit is of great significance for improving their short circuit resistance. The mechanical properties of the insulating pads under different compressive stresses were measured by using a press to perform mechanical property tests on the transformer joint spacers. Therefore, stress–strain tests of the transformer pad and bracket under different compressive stresses were carried out under static and cyclic dynamic loads. To ensure the accuracy of the test results, three parallel experiments were carried out, and the average elastic modulus of the insulating pad was finally obtained. Next, a 3D simulation model of the transformer was established based on the finite element method. The elastic modulus value of the transformer insulating pad block obtained through the experiment was substituted into the finite element simulation model, and the transient field was used to calculate the leakage magnetic field and stress of the winding, in order to study the radial and axial short-circuit electromagnetic forces of each line cake under high-voltage operation and low-voltage short-circuit conditions. The distribution of the leakage field and the calculated electromagnetic force at key points of the winding were analyzed, and the stress and displacement distribution of the transformer winding under different compression stresses was further calculated. The influence of different compression stresses on the transformer insulating pad and its mechanical properties on the transformer winding was explored through simulation calculations. It can be found that as the compressive stress on the transformer insulating pad block increases, the elastic modulus gradually increases, while the stress and displacement on the winding gradually decrease. Therefore, when selecting a transformer insulating pad block, priority should be given to a block with a higher elastic modulus, which will have a positive impact on the mechanical properties of the winding.