The invention provides a defense checking method and device for a short circuit accumulated effect of a power transformer, and aims at providing the accumulated short circuit checking calculation method which can reflect difference in accumulated effect tolerance and anti-short-circuit capability of devices and can be related to multiple times of short circuit in a service life of the power grid, so that work demands for equipment reliability prediction and life pre-estimation can be met. The method comprises that a predetermined current value of a multi-time short circuit accumulated effect of the power transformer is compared with a short-circuit current tolerance value prescribed by a preset national standard to determine an accumulation effect coefficient; a bearable short-circuit current value is calculated according to the accumulation effect coefficient and a preset electromagnetic simulation mode; and according to the accumulation effect coefficient and a possible short circuit frequency, a short-circuit current capability of a defense accumulated effect of the transformer is determined.