This article introduces a transformer test prototype with a mouth-shaped iron core and a double-column structure. Each column contains three coils: low-voltage inner, high-voltage, and low-voltage outer. These two low-voltage coils can simulate the amplitude and axial deformation of real transformer coils. The article first uses simulations to predict the short-circuit withstand current and failure mode of windings under short-circuit impulse. Based on these results, tests were conducted on the model transformer to study the deformation and failure process of the two low-voltage coils. Multiple short-circuit impulse tests were conducted on the coils of the model transformer, during which the short-circuit impedance of the transformer were measured and analyzed. The experimental results show that the short-circuit impedance of the transformer increases monotonically with the increase of the number of shocks, and there will be a sudden increase in short-circuit impedance after a certain shock, indicating that irreversible permanent deformation has occurred at this time. The disassembly inspection of the model transformer after the experiment verified the experimental effect, indicating that the change rate of the transformer’s short-circuit impedance can effectively reflect the deformation of the coil, making it a comparatively effective method for predicting the transformer’s short-circuit resistance capability.