Abstract: In this paper,the transient characteristics of the short-circuit fault of dry-type air-core reactor are studied,and an early-warning method is proposed.The dynamic physical process of dry air core reactor from normal working condition to turn-to-turn short circuit fault condition is analyzed.Based on the ANSYS Maxwell software platform,a transient field circuit coupling calculation model for reactor turn-to-turn short-circuit is established.The transient characteristics of the short-circuit faults of the reactor are analyzed by simulation,and the experimental verification is carried out by setting up the experimental platform.The research shows that in the early stage of the reactor short-circuit fault,the instantaneous formation of the short-circuit ring will cause a sudden change in the magnetic field at the short-circuit position of the reactor,and the induced voltage of the magnetic field detecting coil mounted on the outer surface of the reactor will be significantly abnormally changed.According to this,an early warning can be made in the early stage of the reactor short-circuit fault.