Abstract: In the scenario of the global energy structure undergoing accelerated adjustments and new energy being massively integrated, harmonic pollution has emerged as a factor exacerbating the stability issues of power systems. Filter transformers, as crucial equipment for harmonic mitigation, demand high operational reliability. This paper centers on a three-phase short-circuit fault that occurred at the site of a particular filter transformer. It dissects the structural features and short-circuit checking methods of this transformer, and conducts in-depth research on its short-circuit mechanical properties. The research findings uncover the force-bearing characteristics and failure mechanisms of the filter windings during short-circuit conditions. These results serve as a significant foundation for the optimal design of filter transformers, ensuring their safe operation, and promoting the stable development of new-generation power systems.