Despite Jiles-Atherton (J-A) hysteresis theory has been widely used in the analysis of magnetic properties of iron core components in electric power equipment, the transient modeling of switching device considering hysteresis characteristics remains more challenging given that most electromagnetic transient simulation software lacks a practical dynamic J-A hysteresis inductor model. A J-A hysteresis inductor model considering the iron core's dynamic loss was developed with the Electromagnetic Transients Program-Alternative Transients Program (EMTP-ATP) in this study. The classical J-A hysteresis theory was first modified from the perspective of energy conservation equation. Then, the differential equations of the J-A hysteresis model considering dynamic loss were derived according to the field separation and statistical theory of losses, and the final J-A model parameters were determined by particle swarm optimization (PSO) algorithm. The modified dynamic J-A hysteresis model was programmed by Model Language using the Type-94 component in EMTP-ATP, thereby obtaining a dynamic J-A hysteresis inductor model that can be used for electromagnetic transient simulation. The proposed model was verified by sinusoidal excitation test and harmonic excitation simulation. The results show that the excitation simulation outcomes of the dynamic J-A hysteresis inductor model were well fit in the measured data, and it could work stably under harmonic excitation condition, which verifies the feasibility of this model.